Purification, structure, and characterization of caltrin proteins from seminal vesicle of the rat and mouse.

Caltrins, small basic proteins that inhibit calcium uptake by epididymal spermatozoa, have been purified from seminal vesicle content of the mouse and rat. Mouse caltrin (M(r) 8,476) contains 75 amino acid residues, 14 basic, 5 acidic, and 7 cysteines while rat caltrin (M(r) 6,217) has 56 residues, 10 basic, 5 acidic, and 6 cysteines; their pI values are 10.2 and 9.3, respectively. The proteins did not react with Ellman's reagent unless the cystine residues were previously reduced. The primary structures were determined by sequencing fragments generated by trypsin, clostripain, and endoproteinase Lys-C digestion. The sequences were ordered to give the total structural formula. The two molecules have no sequence similarity and are different from those of the bull and guinea pig previously reported. Only rat caltrin has a sequence of 13 residues nearly identical to that in guinea pig caltrin I. Both rat and mouse caltrin react with antibodies against bovine and guinea pig caltrins. Reduction and alkylation of cysteine residues suppressed the immunologic response of mouse caltrin; however, modified rat caltrin retained partially its immunoreactivity with the antiserum against guinea pig caltrin I. The same treatment abolished the calcium transport inhibitory activity of mouse caltrin and greatly reduced that of rat caltrin. It is likely that rat and mouse caltrins have the same physiological function as proposed for bovine caltrin; namely, to regulate the development of the Ca(2+)-dependent processes that "capacitate" sperm for fertilization.     

Functional properties of caltrin proteins from seminal vesicle of the guinea pig.

Caltrin proteins from seminal vesicle content of the guinea pig bind with great specificity to different regions of the spermatozoa. Indirect immunofluorescence studies with polyclonal antibodies showed that caltrin I binds to the head, on the acrosomal cup, while caltrin II binds on the principal tail and the neck. No fluorescence was detected either in the midpiece or in the post-acrosomal area of the head when sperm were exposed to either of the caltrins. Calcium-induced hyaluronidase release, which occurs during the acrosomal reaction, was dramatically inhibited by caltrin I (approximately 85% inhibition). Caltrin II was less effective in preventing the enzyme release (approximately 50% inhibition). Chemical modification of the structure modified the biological activity of the two caltrins. Reduction and carboxymethylation of the cysteine residues diminished the inhibitory activity on 45Ca2+ uptake and reduced the ability of the proteins to react with their antibodies. Removal of the carbohydrate portion by chemical deglycosylation transformed the inhibitor proteins into enhancers of calcium uptake into the spermatozoa. Caltrin proteins from the guinea pig appear to play the same physiological role as bovine caltrin, regulating specifically calcium transport across the spermatozoal membranes related with the acrosome reaction and hyperactivation process. The dual behavior of caltrins to inhibit or enhance Ca2+ uptake enables them to fulfill this function. Nevertheless, molecular mechanisms different from those described for bovine caltrin seem to be involved in the control of the functional activity of the guinea pig caltrins.     

Trypsin/acrosin inhibitor activity of rat and guinea pig caltrin proteins. Structural and functional studies

Dramatic inhibition of trypsin activity by rat caltrin and guinea pig caltrin I was spectrophotometrically demonstrated using the artificial substrate benzoylarginyl ethyl ester. Approximately 6% and 21% of residual proteolytic activity was recorded after preincubating the enzyme with 0.22 and 0.27 microM rat caltrin and guinea pig caltrin I, respectively. Reduction and carboxymethylation of the cysteine residues abolished the inhibitor activity of both caltrin proteins. Rat caltrin and guinea pig caltrin I show structural homology with secretory trypsin/acrosin inhibitor proteins isolated from boar and human seminal plasma and mouse seminal vesicle secretion and share a fragment of 13 amino acids of almost identical sequence (DPVCGTDGH/K/ITYG/AN), which is also present in the structure of Kazal-type trypsin inhibitor proteins from different mammalian tissues. Bovine, mouse, and guinea pig caltrin II, three caltrin proteins that have no structural homology with rat caltrin or guinea pig caltrin I, lack trypsin inhibitor activity. Rat caltrin, guinea pig caltrin I, and the mouse seminal vesicle trypsin inhibitor protein P12, which also inhibits Ca(2+) uptake into epididymal spermatozoa (mouse caltrin I), bound specifically to the sperm head, on the acrosomal region, as detected by indirect immunofluorescence. They also inhibited the acrosin activity in the gelatin film assay. Caltrin I may play an important role in the control of sperm functions such as Ca(2+) influx in the acrosome reaction and activation of acrosin and other serine-proteases at the proper site and proper time to ensure successful fertilization.     

Identification and partial characterization of caltrin-like proteins in the reproductive tract of the guinea pig

The presence of caltrin-like proteins in reproductive tract fluid (RTF) and seminal vesicle content from male guinea pigs has been determined. Two fractions with electrophoretic mobility corresponding to Mr = 6200 (main band) and 5100 were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting. Isoelectric focusing in thin-layer agarose gels revealed three bands with acidic pIs of 5.3, 6.0, and 6.2, respectively. RTF prevented the enhancement of calcium permeability induced by incubating guinea pig epididymal spermatozoa in medium for capacitation. Spermatozoa incubated for 2 h in minimal culture medium plus pyruvate and lactate containing RTF accumulated less than 30% of the 45Ca2+ accumulated by cells maintained in absence of this fluid. Calcium uptake by preincubated spermatozoa was also inhibited by RTF. Inhibition of calcium transport activity by RTF and seminal vesicle proteins was not decreased by heating the dialyzed preparations at 60 degrees C for 5 min. After this treatment, the inhibitory activity and the protein pattern were stable for 3 wk when stored at 4 degrees C. Unheated extracts lost calcium transport inhibitory activity after 2 or 3 days at 4 degrees C. In spite of the differences in pIs among the proteins from the guinea pig reproductive tract and bovine caltrin, several features indicate they may play a similar role in both species by controlling Ca2+ movement across the plasma membrane. By this mechanism, these proteins could regulate physiologic events essential for the fertilization process.     

Sequence of Guinea Pig Myelin Basic Protein

This paper proposes a tentative amino acid sequence of guinea pig myelin basic protein obtained by comparison of peptide fragments of the guinea pig and bovine proteins. Analyses of the tryptic peptides confirmed the known sequence differences in the NH2-terminal half of the molecule and showed that in the COOH-terminal half of the guinea pig protein Ser131 was missing, Ala136 - His137 was deleted, Leu140 was replaced by Phe, and an extra Ala was inserted somewhere within sequence 142-151 (tryptic peptide T23 ). Sequence determination of guinea pig tryptic peptides corresponding to residues 130-134 ( T20 ), 135-138 ( T21 ), and 142-151 ( T23 ) of the bovine protein confirmed the above sequence changes and placed the extra Ala between Gly142 and His143 . The sequence of the region corresponding to bovine residues 130-143 is thus Ala-Asp-Tyr-Lys-Ser-Lys-Gly-Phe-Lys-Gly-Ala-His. No species differences were observed in the amino acid compositions of the remaining tryptic peptides obtained from the COOH-terminal half of the molecule. Based upon these results, the guinea pig basic protein contains 167 amino acid residues and has a molecular weight of 18,256.     

Androgen-dependent expression, gene structure, and molecular evolution of guinea pig caltrin II, a WAP-motif protein

We determined the cDNA and gene structures of guinea pig caltrin II, a unique member of the calcium transporter inhibitors containing a whey acidic protein (WAP) motif, and we established that it is a secretory protein with a potential 21-amino acid signal peptide in its N-terminus. Northern blot analysis and in situ hybridization histochemistry indicated that the expression of caltrin II is restricted to luminal epithelial cells in the seminal vesicles. Its message levels markedly decreased either after castration (and were restored by simultaneous administration of testosterone) or after treatment of the animals with estradiol, suggesting that the expression of caltrin II is androgen-dependent. Recombinant caltrin II had an elastase-inhibitor activity. Comparison of sequence between the caltrin II and related genes and their molecular evolutionary analyses revealed that caltrin II and seminal vesicle secretory proteins (SVPs) appear to be evolved from a common ancestor gene that is made by the fusion of semenogelin and trappin genes. Caltrin II and SVPs lost the transglutaminase substrate domain and the WAP motif, respectively, within a single exon, resulting in the exertion of different functions.     

Demonstration of apolipoprotein CII in guinea pigs. Functional characteristics, cDNA sequence, and tissue expression

In contrast to plasma from other mammals, guinea pig plasma does not stimulate the activity of lipoprotein lipases in vitro. This had led previously to the conclusion that guinea pigs lack an analogue to apolipoprotein CII (apoCII). By adsorption of lipid-binding proteins to lipid droplets, thereby separating them from other plasma components, we could demonstrate apoCII-like activity in guinea pig plasma. On electrophoresis, the CII-like activity co-migrated with one isoform of guinea pig apolipoprotein CIII, identified by amino-terminal amino acid sequence determination (40 residues). By isoelectric focusing in a narrow pH gradient, the activating protein was separated sufficiently from the dominating apoCIII isoform to allow sequence determination of 8 residues from the amino terminus. Six of these were identical to corresponding residues in apoCII from dog and monkey. With the aid of a human apoCII cDNA probe we identified one cross-hybridizing mRNA species (approximately 600 nucleotides) on Northern blots of guinea pig liver. Three positive clones were isolated from a guinea pig liver cDNA library using the same cDNA probe. The nucleotide sequence showed extensive similarities to the previously known human, monkey, and canine sequences, but the signal peptide was 3 amino acid residues longer in the guinea pig protein, and there was a deletion of 4 residues in the putative lipid binding domain. Northern blot analyses indicated that guinea pig apoCII is mainly expressed in the liver with little or no contribution from the intestine.     

Proteinase isoinhibitors from bovine spleen: primary structure of an intermediate in the processing of the precursor

The complete amino acid sequence of the proteinase inhibitor III from bovine spleen is reported. It consists of 62 amino acid residues and is identical to that of spleen inhibitor II (an isoinhibitor of the bovine pancreatic trypsin inhibitor, which shares with the latter 89% of sequence identity), except for four extra residues at the C-terminal side. Inhibitor III appears to be an intermediate in the processing of the putative 100-residue primary expression product, which leads to the mature inhibitor II. These results and those previously obtained for another intermediate, isoinhibitor I, are indicative of the following order for the last steps of the precursor processing inhibitor I----inhibitor III----inhibitor II. The mature protein and the two intermediates isolated have a very similar antiproteolytic activity. However, their in vivo target enzyme(s) are not yet known, as also the target enzyme of the bovine pancreatic trypsin inhibitor is not known. Thus, the available data would indicate that either the three isoinhibitors have a distinct functional role, by inhibiting different target enzymes, or inhibitors I and III are obligatory intermediates for directing the final targeting of the mature, functionally relevant inhibitor II.     

Sites in Myelin Basic Protein that React with Monoclonal Antibodies

The epitopes (antigenic sites) for seven monoclonal antibodies (MAbs) evoked in rats or mice by guinea pig or monkey myelin basic protein (BP) have been located in four different sequences of the BPs extracted from various species. Six of the MAbs were evoked by guinea pig BP. (1) One epitope, possibly a pair, is included within residues 1-14 of all BPs tested and reacts with two rat IgG MAbs. (2) A definite pair of overlapping epitopes includes the central Phe91-Phe92 sequence. One epitope is contained entirely within sequence 90-99 and reacts with a rat IgG MAb. The substitution of Ser in chicken BP for Thr97 destroys this epitope. The other epitope appears to include residues on the amino side of Phe44 and even of His32 and suggests some tertiary structure in BP. This epitope reacts with a mouse IgM MAb that does not recognize the chicken substitution. (3) The third epitope lies within residues 114-121, specifically including Trp118, and reacts with a rat IgG MAb. A cross-reacting epitope probably includes residues 44-45 in certain species (guinea pig and bovine but not rabbit). (4) Another pair of epitopes is located within residues 131-140 but is severely species-restricted. This region in guinea pig BP evoked a species-specific mouse IgM MAb. The same region in monkey BP evoked the seventh MAb, a mouse IgG, which reacts with human, chimpanzee, monkey, bovine, and rat-18.5 kDa BPs and to a lesser extent rabbit BP but not with guinea pig, pig, or chicken BPs. Some tertiary structure in guinea pig BP is also suggested by the reactivities with the IgM MAb. All of the MAbs react with myelin in histologic preparations, but the optimum method of preparation of the tissue varies with each.     

Studies on the Wolfgram High Molecular Weight CNS Myelin Proteins: Relationship to 2'',3''-Cyclic Nucleotide 3''-Phosphodiesterase

Evidence is presented that the major protein components of the high molecular weight CNS myelin proteins designated as the Wolfgram protein doublet (W1 and W2) contain the enzyme 2',3'-cyclic nucleotide 3'-phosphodiesterase (EC 3.1.4.37, CNP). CNP is a basic hydrophobic protein containing about 830 to 840 amino acid residues. When electrophoresed on SDS polyacrylamide gels, CNP appears as a protein doublet, separated by a molecular weight difference of about 2500-3000 in bovine, human, rat, guinea pig, and rabbit. A similar protein doublet has been identified as the Wolfgram proteins W2 and W1 in myelin and in the chloroform-methanol-insoluble pellet obtained from myelin. Moreover, the relative Coomassie blue staining intensity of the CNP2 plus CNP1 protein doublet among the species examined was remarkably similar to that observed for electrophoresed myelin and chloroform-methanol-insoluble pellet derived from myelin. Antisera raised against purified bovine CNP recognized the W1 and W2 proteins isolated from bovine and human brain. The amino acid composition of pure bovine CNP is presented and compared with the compositions of several rat and bovine Wolfgram proteins obtained by other investigators. Our electrophoretic, compositional, and immunological data support the contention that the enzyme CNP is a major component of the Wolfgram protein doublet.     

Cationic proteins of polymorphonuclear leukocyte lysosomes. II. Composition, properties, and mechanism of antibacterial action

Zeya, H. I. (University of North Carolina, Chapel Hill), and J. K. Spitznagel. Cationic proteins of polymorphonuclear leukocyte lysosomes. II. Composition, properties, and mechanism of antibacterial action. J. Bacteriol. 91:755-762. 1966.-A basic proteins fraction from guinea pig polymorphonuclear (PMN) granules was obtained by acid extraction and precipitation with 20% (v/v) ethyl alcohol. The fraction accounted for most of the antibacterial activity of the PMN granules and corresponded to the antibacterial cationic components of intact granules (bands I, II, and III) resolved by zone electrophoresis. Absence from the fraction of components identical to the enzymatic components of intact lysosomes showed that the fraction was essentially free from lysosomal enzymes. The amino acid analysis of proteins in the fraction gave a preponderance of basic amino acids (25%), especially of arginine (16%). The comparative amino acid analysis showed that the lysosomal cationic proteins (LCP) fraction was markedly different from nuclear histones. The LCP fraction manifested antibacterial activity against certain gram-positive and gram-positive microorganisms, including Candida albicans, and exhibited stoichiometric relationship in its activity. Microorganisms treated with LCP fraction were agglutinated. Anionic substances such as nucleic acids, heparin, and endotoxin effectively blocked the antibacterial activity of the fraction. The LCP fraction caused suppression of oxygen uptake by bacterial cells and damaged the permeability barriers of cells as manifested by rapid release of P(32) as well as ultraviolet-absorbing material at 260 mmu, in the supernatant fluid.     

Purification, composition, and structure of macrophage adhesion molecule

Macrophage adhesion molecule (MAM) is a surface heterodimer consisting of the trypsin- and plasmin-sensitive glycopeptide gp160 (MAM-alpha) and the glycopeptide gp93 (MAM-beta). MAM, which is the guinea pig analogue of Mo1 and Mac-1, was purified from detergent lysates of peritoneal neutrophils by lentil lectin chromatography and M2-antibody chromatography. The pure heterodimer molecule was dissociated by acidic conditions (pH 3.5), and MAM-alpha and MAM-beta were separated by M7-antibody chromatography. MAM-beta is an approximately 640 amino acid residue polypeptide with exceptionally high cysteine content. At 7.2 residues per 100 amino acids, Cys/2 of MAM-beta is more than 3 times the mean for 200 purified proteins. Reactivity with six beta-subunit-specific monoclonal antibodies recognizing at least four epitopes demonstrated that intrapeptide disulfide bonds are required to maintain the structure of MAM-beta. All six antibodies failed to react when MAM-beta was treated with reducing agents. MAM-beta is 18% carbohydrate; the major monosaccharides are mannose, N-acetylglucosamine, galactose, and sialic acid. MAM-beta is estimated to contain five to six N-linked carbohydrate units. MAM-alpha is an approximately 1100-residue polypeptide with lower Cys/2 content (2.0 residues per 100 amino acid residues). MAM-alpha is 21% carbohydrate. The major monosaccharides are mannose, N-acetylglucosamine, galactose, and sialic acid; the mannose content is higher in MAM-alpha than MAM-beta. MAM-alpha is estimated to contain 12 N-linked carbohydrate units.     

Structure-activity studies of heptapeptide derivatives related to substance P, neurokinin A, B and other tachykinins on smooth muscles

Diverse C-terminal heptapeptide derivatives related to substance P, kassinin, physalaemin, neurokinin A and B were synthesized and the contracting activities on the guinea pig ileum as well as rat duodenum were compared. In the partial sequence of C-terminal of tachykinin peptides, -I-II-Phe-III-Gly-Leu-Met-NH2, the combination of amino acid residues at positions I and III have significant roles in contraction of smooth muscle. For the activation of rat duodenal muscle (SP-E), Asp(I) and aliphatic amino acid(III), and for guinea pig ileal muscle(SP-P), Gln(I) and aromatic amino acid(III) are essential. Moreover, guinea pig ileum is sensitive to a full sequence of neurokinin peptides.     

Primary structure of a protease isoinhibitor from bovine spleen. A possible intermediate in the processing of the primary gene product

Sequence studies on the protease isoinhibitor I isolated from bovine spleen have revealed that it consists of two molecular variants which differ only in the presence of an additional COOH-terminal residue, asparagine, in the less abundant form. The complete amino acid sequence shows that they are composed of 65 or 66 residues and predicts Mr of 7223 or 7338, respectively. The sequences correspond exactly to the 58-residue polypeptide chain of spleen isoinhibitor II plus NH2- and COOH-terminal extensions of 2 and 5 or 6 amino acid residues, respectively. Moreover the entire sequences are located within the 100-residue structure deduced from the mRNA and DNA sequences of the putative precursor. These data support the idea that the molecular variants of isoinhibitor I are either mature proteins with distinct functional roles, or intermediates in the multistage processing of the primary product of gene expression, which eventually leads to the mature protein, i.e. inhibitor II.     

The major erythrotropin of bovine Cohn fraction V has the N-terminal sequence of insulin-like growth factor II with isoleucine at position 35

The major erythrotropin-like factor of bovine Cohn Fraction V has been isolated from commercial albumin preparations by reversed-phase HPLC. The N-terminal sequence of the major fraction with erythrotropin-like activity is practically identical to the sequence of bovine insulin-like growth factor II. Within the first 45 amino acids, the only difference was the presence of an isoleucine instead of a serine at amino acid 35. This substitution may affect the immunoreactivity of this peptide using antibodies against bovine or human insulin-like growth factor II.     

Properties and function of caltrin, the calcium-transport inhibitor of bull seminal plasma

Indirect immunofluorescence studies with polyclonal antibodies show that caltrin binds to the plasma membrane over the acrosome and principal tail regions of bovine spermatozoa but not to the postacrosomal area or the midpiece. Calcium influx into bovine epididymal spermatozoa maintained in a simple salt medium containing DL-beta-hydroxybutyrate is prevented by caltrin freshly prepared from bovine seminal plasma through a procedure employing only gel permeation columns. Older preparations, on the other hand, enhance calcium uptake into these cells. Caltrin freshly prepared through a purification scheme that includes a cation exchanger only induces enhancement of calcium uptake into bovine epididymal spermatozoa maintained under identical conditions. It is postulated that early during sperm transit through the female reproductive tract, caltrin bound to the sperm plasma membrane protects the sperm cells from calcium influx. As the cells enter the oviduct where meeting with the egg could take place, factors present in the surrounding milieu may cause caltrin to change from an inhibitor to an enhancer of calcium uptake. The acrosome reaction and possibly hyperactivation, two components of capacitation that require calcium influx as an initial event, then take place.     

Molecular cloning and sequence analysis of cDNAs coding for guinea pig alpha 1-antiproteinases S and F and contrapsin

The cDNAs encoding two isoforms, S (slow) and F (fast), of alpha 1-antiproteinase (also referred to as alpha 1-antitrypsin or alpha 1-proteinase inhibitor) as well as contrapsin were obtained by screening lambda gt11 cDNA library prepared fro inflamed guinea pig liver. The sequence analyses of these cDNAs and NH2-terminal peptides of the purified proteins revealed that both isoforms of alpha 1-antiproteinase consist of 405 amino acid residues including a signal peptide of 24 residues and that contrapsin consists of 410 amino acid residues with the same length of the signal peptide. Guinea pig contrapsin had 89, 88, 62, 42, and 41% homology to its own alpha 1-antiproteinases F and S, rat alpha 1-antiproteinase, mouse and rat contrapsins, respectively. This suggests that guinea pig contrapsin is not orthologous to mouse and rat contrapsins and that it developed from a much later duplication of alpha 1-antiproteinase gene after the guinea pig had diverged from the murine lineage. The available data suggest that the reactive site region of alpha 1-antiproteinase can be categorized into orthodox and unorthodox types: the former has P3-P'3 consensus sequence of Xaa-Pro-Met-Ser-Xaa-Pro, where Xaa is Leu, Ile, Val, or Met, while the latter, which occurs in species having multiple alpha 1-antiproteinase isoforms, has the sequence whose P1 Met has changed to other amino acids. Thus, the reactive site region of the orthodox type, which occurs in all seven mammals examined to date, is highly conserved. This is in marked contrast to the fact that the same region is hypervariable among the paralogous proteins belonging to the serpin superfamily.     

Isolation and partial characterization of the major apolipoprotein component of bovine serum high density lipoprotein.

The delipidated protein component of bovine serum high density lipoprotein was fractionated by gel filtration on a Sephadex G-150 column (equilibrated with buffer containing 6 M urea) into three fractions: I, II and III. Fractions I and II together constitute 88% of all the protein weight of bovine high density lipoprotein, whereas fraction III accounts for the remaining 12%. Analysis of the fractions by sodium dodecyl sulfate-polyacrylamide electrophoresis reveals that fraction I consists mostly of aggregated forms of fraction II and some higher molecular weight species, probably irreversible aggregates of fraction II. The irreversible aggregates are apparently formed during the delipidation procedure or upon aging of the lipoprotein. The major protein component of the high density bovine lipoprotein is found in fraction II; it has a molecular weight of 27 000 plus or minus 1500 and appears to be homogeneous by several physicochemical criteria. The amino acid composition of fractions I and II are essentially identical; their spectral properties, including absorption, fluorescence, and circular dichroism spectra, are similar; however, fraction I appears to contain traces of oxidized lipid and more secondary alpha-helical organization than fraction II. By comparison with the intact lipoprotein, which contains about 65% of alpha-helical structure, fractions I and II have diminished alpha-helical organization, 55% and 43%, respectively. Fraction III, on sodium dodecyl sulfate-polyacrylamide electrophoresis, separates into two protein bands of equivalent intensity, having molecular weights around 13 000 and 11 000. Fraction III is markedly distinct from the other two, in amino acid composition and spectral properties, especially in its red-shifted fluorescence and very low content of alpha-helical structure. The protein composition of bovine serum high density lipoprotein is compared with recently published results for high density lipoprotein apoproteins of man, chimpanzee, rhesus monkey, pig and rat. Similarities and differences are discussed in terms of possible evolutionary and functional factors.     

Apolipoprotein CIII from guinea pig (Cavia porcellus) is shorter and less homologous than apolipoprotein CIII from other mammals

Apolipoprotein (apo) CIII plays an important role in metabolism of triglyceride-rich lipoproteins as a regulator of lipolysis and/or lipoprotein-receptor interaction. With the method of RT-PCR, the cDNA of guinea pig apo CIII was cloned and sequenced. The deduced amino acid sequence of 91 amino acids residues consists of a highly conserved signal peptide of 20 residues and a mature protein of 71 residues. Compared to mouse, rat, dog, bovine and human apo CIII, guinea pig apo CIII has a deletion of eight or nine amino acids at its C-terminus and it shows the lowest degree of homology to the presently known apo CIII sequences. Interestingly, the most conserved areas of guinea pig apo CIII are found in two regions, residues 16-33 and residues 50-69. Corresponding regions in human and dog apo CIII were previously predicted to form amphipathic helices, which are assumed to play important roles in the inhibition of lipoprotein lipase (LPL) and binding to lipid. Our present study could be helpful for the future elucidation of the structure-function relationships and evolution of apo CIII.     

COMPARATIVE STUDIES OF GUINEA PIG AND BOVINE MYELIN BASIC PROTEINS. PARTIAL CHARACTERIZATION OF CHEMICALLY DERIVED FRAGMENTS AND THEIR ENCEPHALITOGENIC ACTIVITIES IN LEWIS RATS

Guinea pig and bovine myelin basic proteins were chemically cleaved at the carboxyl peptide bonds of methionyl and tryptophanyl residues to yield several fragments. Comparison of the bovine fragment consisting of the first 20 residues of the protein with the corresponding guinea pig fragment showed that the latter differs in containing histidine and glycine (one residue of each), an additional threonyl residue, and one fewer alanyl residues. Comparison of the bovine fragment consisting of the C-terminal 54 residues of the protein (residues 117-170) with the corresponding guinea pig fragment showed that the latter differs in containing one fewer histidyl and leucyl residues and an additional phenylalanyl residue. Tests of encephalitogenic activity in Lewis rats showed that these two fragments from both species were much less active, on a molar basis, than the uncleaved protein. On the other hand, examination of the bovine fragments consisting of residues 1-116 and 21-116 and the corresponding fragments obtained from the guinea pig protein revealed activity at least as high as that of the respective uncleaved proteins.