Gamma-crystallin genes in carp: cloning and characterization.

The carp gamma-crystallin gene family was found to be composed of at least three members: gamma m1, gamma m2 and gamma m3. The encoded products are very similar to other known gamma-crystallins but with their own peculiarities: (1) they all have a high methionine content: 12.4%, 14% and 8.4% in gamma m1, gamma m2 and gamma m3, respectively; and (2) the amino acid sequences are aberrant in the region before connecting peptides and its corresponding region in motif 4. Their protein structures might remain the same as those of other gamma-crystallins since they retain all the conserved amino acid residues essential for maintaining the loops in the protein structures.     

Predicted secondary and tertiary structures of carp gamma-crystallins with high methionine content: role of methionine residues in the protein stability.

A systematic structural comparison of several carp gamma-crystallins with high methionine contents was made by the secondary-structure prediction together with computer model-building based on the established X-ray structure of calf gamma-II crystallin. The overall surface hydrophilicity profile and the distribution of helices, beta-sheets, and beta-turns along the polypeptide chains are very similar among these carp gamma-crystallins. In addition, their general polypeptide packing is close to the characteristic 2 domain/4 motif Greek key three-dimensional conformation depicted for the calf gamma-II crystallin. Interestingly, most hydrophobic methionine residues are located on the protein surface with only a few buried inside the protein surface or in the interface between two motifs of each domain. The exposed hydrophobic and polarizable methionine cluster on the protein surface may have a bearing on the crystallin stability and dense packing in the piscine species, and probably also provides a malleable nonpolar surface for the interaction with other crystallin components for the maintenance of a clear and transparent lens.     

Rat lens beta-crystallins are internally duplicated and homologous to gamma-crystallins

The nucleotide sequence of two cloned rat lens beta-crystallin cDNAs pRL beta B3-2 and pRL beta B1-3 has been determined. pRL beta B3-2 contains the complete coding information for a beta-crystallin, designated beta B3, of 210 amino acid residues. pRL beta B1-3 is incomplete at its 5' end; the 5' codogenic information which is not present in this cDNA clone was deduced from the cloned gene. pRL beta B1-3 codes for a beta-crystallin polypeptide, designated beta B1, whose full length is 247 amino acid residues. Considerable sequence homology is noted between the amino- and carboxy-terminal halves of each protein. The two rat beta-crystallins show a substantial sequence homology with each other (60%) as well as with the published sequences of rat gamma-crystallin (37%) and bovine and murine beta-crystallins (55 and 45%). All these proteins have a two-domain structure which, like the bovine gamma II-crystallin, might be folded into four remarkably similar protein motifs. Our data further indicate that the beta-crystallins can be subdivided into two groups which are evolutionarily related. Both groups are, although more distantly, also related to the gamma-crystallins.     

Identification of methionine Nalpha-acetyltransferase from Saccharomyces cerevisiae

N alpha-Acetylation is the most frequently occurring chemical modification of the alpha-NH2 group of eukaryotic proteins and was believed until now to be catalyzed by a single N alpha-acetyltransferase. The transfer of an acetyl group from acetyl coenzyme A to the alpha-amino group of five NH2-terminal residues (serine, alanine, methionine, glycine, and threonine) in proteins accounts for approximately 95% of acetylated residues. We have found that a crude lysate from Saccharomyces cerevisiae mutant (aaa1) deficient in N alpha-acetyltransferase activity can effectively transfer an acetyl group to peptides containing NH2-terminal methionine but not to serine or alanine. This methionine N alpha-acetyltransferase has been extensively purified, and this purified enzyme can selectively transfer an acetyl group to various model peptides containing an NH2-terminal methionine residue and a penultimate aspartyl, asparaginyl, or glutamyl residue. Such specificity of N alpha-acetylation of methionine has been previously observed based on the analysis of eukaryotic protein sequences (Persson, B., Flinta, C., Heijne, G., and Jornvall, H. (1985) Eur. J. Biochem. 152, 523-527; Arfin, S.M., and Bradshaw, R. A. (1988) Biochemistry 27, 7979-7984). The indentification of this methionine N alpha-acetyltransferase provides an explanation as to why two distinct classes of N alpha-acetylated proteins exist in nature: (i) those whose initiator methionine is acetylated and (ii) those whose penultimate residue is acetylated after cleavage of the initiator methionine.     

Evolutionary conservatism of the molecular structure of gamma-crystallins of vertebrates

Homology of 18 amino acid sequences of lens gamma-crystallins of several vertebrates: frog, mouse, rat, calf and human being--has been considered. Pair sequence homology varies in the range from 57 to 100%, the mean value is equal to 74%. The spatial structures have been determined only for two calf gamma-crystallins. The protein molecule consists of four-fold repeated "motifs" (patterns) which are joint in two domains. After comparison of 18 gamma-crystallin sequences it was found that "motifs" domains and whole protein molecules have about 10, 30 and 58% conservative residues, respectively, that seem to be related to the evolution of these structural units. Structure analysis shows that almost all the conservative residues have an important structural meaning and play a basic role in the domain and molecular structure organization. This result allows us to make a conclusion about the homology of spatial structures of all considered gamma-crystallins of vertebrates.     

Phylogenetic analysis of <Emphasis Type="Italic">Brassiceae</Emphasis> based on the nucleotide sequences of the <Emphasis Type="Italic">S</Emphasis>-locus related gene, <Emphasis Type="Italic">SLR1</Emphasis>

Nucleotide sequences of orthologs of the S-locus related gene, SLR1, in 20 species of Brassicaceae were determined and compared with the previously reported SLR1 sequences of six species. Identities of deduced amino-acid sequences with Brassica oleracea SLR1 ranged from 66.0% to 97.6%, and those with B. oleracea SRK and SLR2 were less than 62% and 55%, respectively. In multiple alignment of deduced amino-acid sequences, the 180-190th amino-acid residues from the initial methionine were highly variable, this variable region corresponding to hypervariable region I of SLG and SRK. A phylogenetic tree based on the deduced amino-acid sequences showed a close relationship of SLR1 orthologs of species in the Brassicinae and Raphaninae. Brassica nigra SLR1 was found to belong to the same clade as Sinapis arvensis and Diplotaxis siifolia, while the sequences of the other Brassica species belonged to another clade together with B. oleracea and Brassica rapa. The phylogenetic tree was similar to previously reported trees constructed using the data of electrophoretic band patterns of chloroplast DNA, though minor differences were found. Based on synonymous substitution rates in SLR1, the diversification time of SLR1 orthologs between species in the Brassicinae was estimated. The evolution and function of SLR1 and the phylogenetic relationship of Brassiceae plants are discussed.     

Biosynthesis of tetrahydrofolate. Sequence of GTP cyclohydrolase I from Escherichia coli.

The sequence of the gene coding for GTP cyclohydrolase I of Escherichia coli and of the adjacent regions was determined. The open reading frame contains 669 nucleotides. The deduced amino-acid sequence represents a protein consisting of 223 amino-acid residues with a molecular mass of 24,873 Da. Partial amino-acid sequences of the N-terminal region and of 5 peptides obtained by trypsin and BrCN cleavage were determined by Edman degradation and were in full agreement with the sequence deduced from the nucleotide sequence. The starting methionine is removed by posttranslational modification. The protein shows extensive homology to the recently reported GTP cyclohydrolase from rats.     

Synthesis of bioactive seminalplasmin by expression of a newly constructed fusion gene

A synthetic DNA, carrying the coding sequence for seminalplasmin (SAP), the major basic protein of bull semen, was cloned into the C-terminal part of a shortened, mutated fragment of the lacZ gene (lacZ-MF) of vector pLZPWB1. As a result of the mutation, all methionine as well as cysteine residues are replaced by other amino-acid residues. In the fusion gene lacZ-MF-SAP of the resulting construct pSAP4 the two proteins are linked through a methionine residue. Expression of pSAP4 in E. coli W3110 in the presence of the inducer isopropylthiogalactoside (IPTG) led to production of fusion protein with a yield of approximately 50% of the total proteins synthesized. All SAP-immunoreactive fusion protein was found within the insoluble protein fraction and represented 40% of total proteins produced during expression. The fusion protein was subjected to cyanogen bromide cleavage. The overall yield of crude SAP with a purity of 80% was 10 mg/l of culture. The crude SAP was further purified by calmodulin-Sepharose affinity absorption. Characterisation by protein chemical analysis indicated the identity of recombinant SAP with authentic SAP purified from bull semen.     

Cloning and sequencing of the genes encoding cyclic tetrasaccharide-synthesizing enzymes from Bacillus globisporus C11

The genes for isomaltosyltransferase (CtsY) and 6-glucosyltransferase (CtsZ), involved in synthesis of a cyclic tetrasaccharide from alpha-glucan, have been cloned from the genome of Bacillus globisporus C11. The amino-acid sequence deduced from the ctsY gene is composed of 1093 residues having a signal sequence of 29 residues in its N-terminus. The ctsZ gene encodes a protein consisting of 1284 residues with a signal sequence of 35 residues. Both of the gene products show similarities to alpha-glucosidases belonging to glycoside hydrolase family 31 and conserve two aspartic acids corresponding to the putative catalytic residues of these enzymes. The two genes are linked together, forming ctsYZ. The DNA sequence of 16,515 bp analyzed in this study contains four open reading frames (ORFs) upstream of ctsYZ and one ORF downstream. The first six ORFs, including ctsYZ, form a gene cluster, ctsUVWXYZ. The amino-acid sequences deduced from ctsUV are similar in to a sequence permease and a sugar-binding protein for the sugar transport system from Thermococcus sp. B1001. The third ctsW encodes a protein similar to CtsY, suggested to be another isomaltosyltransferase preferring panose to high-molecular-mass substrates.     

Genetic and amino-acid analysis of two maize threonine-overproducing,lysine-insensitive aspartate kinase mutants

The aspartate-derived amino-acid pathway leads to the production of the essential amino-acids lysine, methionine, threonine and isoleucine. Aspartate kinase (AK) is the first enzyme in this pathway and exists in isoforms that are feedback inhibited by lysine and threonine. Two maize (Zea mays L.) threonine-overproducing, lysine-insensitive AK mutants (Ask1-LT19 and Ask2-LT20) were previously isolated. The present study was conducted to determine the map location of Ask2 and to examine the amino-acid profiles of the Ask mutants. The threonine-overproducing trait conferred by Ask2-LT20 was mapped to the long arm of chromosome 2. Both mutants exhibited increased free threonine concentrations (nmol/mg dry weight) over wild-type. The percent free threonine increased from approximately 2% in wild-type kernels to 37–54% of the total free amino-acid pool in homozygous mutant kernels. Free methionine concentrations also increased significantly in homozygous mutants. Free lysine concentrations were increased but to a much lesser extent than threonine or methionine. In contrast to previous studies, free aspartate concentrations were observed to decrease, indicating a possible limiting factor in threonine synthesis. Total (free plus protein-bound) amino-acid analyses demonstrated a consistent, significant increase in threonine, methionine and lysine concentrations in the homozygous mutants. Significant increases in protein-bound (total minus free) threonine, methionine and lysine were observed in the Ask mutants, indicating adequate protein sinks to incorporate the increased free amino-acid concentrations. Total amino-acid contents (nmol/kernel) were approximately the same for mutant and wild-type kernels. In five inbred lines both Ask mutations conferred the threonine-overproducing phenotype, indicating high expressivity in different genetic backgrounds. These analyses are discussed in the context of the regulation of the aspartate-derived amino-acid pathway.     

Unique features of the hemoglobin system of the Antarctic notothenioid fish Gobionotothen gibberifrons.

The hemolysate of the Antarctic teleost Gobionotothen gibberifrons (family Nototheniidae) contains two hemoglobins (Hb 1 and Hb 2). The concentration of Hb 2 (15-20% of the total hemoglobin content) is higher than that found in most cold-adapted Notothenioidei. Unlike the other Antarctic species so far examined having two hemoglobins, Hb 1 and Hb 2 do not have globin chains in common. Therefore this hemoglobin system is made of four globins (two alpha- and two beta-chains). The complete amino-acid sequence of the two hemoglobins (Hb 1, alpha2(1)beta2(1); Hb 2, alpha2(2)beta2(2)) has been established. The two hemoglobins have different functional properties. Hb 2 has lower oxygen affinity than Hb 1, and higher sensitivity to the modulatory effect of organophosphates. They also differ thermodynamically, as shown by the effects on the oxygen-binding properties brought about by temperature variations. The oxygen-transport system of G. gibberifrons, with two functionally distinct hemoglobins, suggests that the two components may have distinct physiological roles, in relation with life style and the environmental conditions which the fish may have to face. The unique features of the oxygen-transport system of this species are reflected in the phylogeny of the hemoglobin amino-acid sequences, which are intermediate between those of other fish of the family Nototheniidae and of species of the more advanced family Bathydraconidae.     

The complete amino-acid sequence of C-phycoerythrin from the cyanobacterium Fremyella diplosiphon

The amino-acid sequences of both subunits of C-phycoerythrin from the cyanobacterium Fremyella diplosiphon have been determined. The alpha-subunit contains 164 amino acid residues, two phycoerythrobilin (PEB) chromophores and has a molecular mass of 18,368 Da (protein: 17,192 Da + 2 PEB, one PEB accounting for 588 Da). The beta-subunit consists of 184 residues, three PEB chromophores and has a molecular mass of 20,931 Da (protein: 19,168 Da and 3 PEB: 1,764 Da). The five PEB chromophores (open chain tetrapyrroles) are covalently bound to six cysteine residues (one of them doubly bound to two cysteine residues). On the alpha-subunit, the first chromophore was found at position 84, homologous to the chromophore binding site of the other biliproteins APC, PC and PEC. The second chromophore, unique for the alpha-subunit of PE, is inserted together with a pentapeptide at position 143 a. On the beta-subunit, a doubly bound chromophore is attached to cysteine residues 50 and 61, similar to the rhodophytan phycoerythrins (B-PE and R-PE). The second and third chromophores were found at positions 84 and 155, homologous to the other biliproteins. A unique peptide insertion of 14 amino acid residues (without chromophore) was found at position 141 a-o in the beta-subunit and probably is located in the three-dimensional model near the additional chromophores of the C-PE alpha- and beta-subunits. Both additional chromophores of the C-PE alpha- and beta-subunit may be located at the periphery of the C-PE-trimer. The amino-acid sequence homology between C-PE alpha- and beta-subunit is 26% and to the alpha- and beta-subunits of C-PC from Mastigocladus laminosus 49% and 48%, respectively.     

Purification, characterization, and cDNA cloning of a novel soluble saxitoxin and tetrodotoxin binding protein from plasma of the puffer fish, Fugu pardalis.

Some species of puffer fish have been reported to possess both of tetrodotoxin and saxitoxin, which share one binding site on sodium channels. We purified a novel soluble glycoprotein that binds to these toxins from plasma of the puffer fish, Fugu pardalis, and named puffer fish saxitoxin and tetrodotoxin binding protein (PSTBP). PSTBP possessed a binding capacity of 10.6 +/- 0.97 nmol x mg(-1) protein and a K(d) of 14.6 +/- 0.33 nm for [(3)H]saxitoxin in equilibrium binding assays. [(3)H]Saxitoxin (10 nm) binding to PSTBPs was half-inhibited by the presence of tetrodotoxin and saxitoxin at 12 microm and 8.5 nm, respectively. From the results of gel filtration chromatography (200 kDa) and SDS/PAGE (104 kDa), PSTBP was suggested to consist of noncovalently linked dimers of a single subunit. PSTBP was completely deglycosylated by glycopeptidase F, producing a single band at 42 kDa. Two highly homologous cDNAs to each other coding PSTBP (PSTBP1 and PSTBP2, the predicted amino-acid identity 93%), were obtained from a cDNA library of F. pardalis liver. These proteins consisted to two tandemly repeated homologous domains. The predicted amino-acid sequences of PSTBP1 and 2 were not homologous to that of saxiphilin, a reported saxitoxin binding protein, or sodium channels, but their N-terminus sequences were homologous to that of the reported tetrodotoxin binding protein from plasma of Fugu niphobles, which has not been fully characterized. The partially homologous cDNA sequences to PSTBP1 and 2 were also found in expressed sequence tag clones of nontoxic flounders liver. Presumably, PSTBP is involved in accumulation and/or excretion of toxins in puffer fish.     

Sequence analysis of alpha 1(VI) and alpha 2(VI) chains of human type VI collagen reveals internal triplication of globular domains similar to the A domains of von Willebrand factor and two alpha 2(VI) chain variants that differ in the carboxy terminus.

Amino acid sequences of human collagen alpha 1(VI) and alpha 2(VI) chains were completed by cDNA sequencing and Edman degradation demonstrating that the mature polypeptides contain 1009 and 998 amino acid residues respectively. In addition, they contain small signal peptide sequences. Both chains show 31% identity in the N-terminal (approximately 235 residues) and C-terminal (approximately 430 residues) globular domains which are connected by a triple helical segment (335-336 residues). Internal alignment of the globular sequences indicates a repetitive 200-residue structure (15-23% identity) occurring three times (N1, C1, C2) in each chain. These repeating subdomains are connected to each other and to the triple helix by short (15-30 residues) cysteine-rich segments. The globular domains possess several N-glycosylation sites but no cell-binding RGD sequences, which are exclusively found in the triple helical segment. Sequencing of alpha 2(VI) cDNA clones revealed two variant chains with a distinct C2 subdomain and 3' non-coding region. The repetitive segments C1, C2 and, to a lesser extent, N1 show significant identity (15-18%) to the collagen-binding A domains of von Willebrand factor (vWF) and they are also similar to some integrin receptors, complement components and a cartilage matrix protein. Since the globular domains of collagen VI come into close contact with triple helical segments during the formation of tissue microfibrils it suggests that the globular domains bind to collagenous structures in a manner similar to the binding of vWF to collagen I.     

Purification and cDNA cloning of a cellulase from abalone Haliotis discus hannai.

A cellulase [endo-beta-1,4-D-glucanase (EC 3.2.1.4)] was isolated from the hepatopancreas of abalone Haliotis discus hannai by successive chromatographies on TOYOPEARL CM-650M, hydroxyapatite and Sephacryl S-200 HR. The molecular mass of the cellulase was estimated to be 66 000 Da by SDS/PAGE, thus the enzyme was named HdEG66. The hydrolytic activity of HdEG66 toward carboxymethylcellulose showed optimal temperature and pH at 38 degrees C and 6.3, respectively. cDNAs encoding HdEG66 were amplified by the polymerase chain reaction from an abalone hepatopancreas cDNA library with primers synthesized on the basis of partial amino-acid sequences of HdEG66. By overlapping the nucleotide sequences of the cDNAs, a sequence of 1898 bp in total was determined. The coding region of 1785 bp located at nucleotide position 56-1840 gave an amino-acid sequence of 594 residues including the initiation methionine. The N-terminal region of 14 residues in the deduced sequence was regarded as the signal peptide as it was absent in HdEG66 protein and showed high similarity to the consensus sequence for signal peptides of eukaryote secretory proteins. Thus, matured HdEG66 was thought to consist of 579 residues. The C-terminal region of 453 residues in HdEG66, i.e. approximately the C-terminal three quarters of the protein, showed 42-44% identity to the catalytic domains of glycoside hydrolase family 9 (GHF9)-cellulases from arthropods and Thermomonospora fusca. While the N-terminal first quarter of HdEG66 showed 27% identity to the carbohydrate-binding module (CBM) of a Cellulomonas fimi cellulase, CenA. Thus, the HdEG66 was regarded as the GHF9-cellulase possessing a family II CBM in the N-terminal region. By genomic PCR using specific primers to the 3'-terminal coding sequences of HdEG66-cDNA, a DNA of 2186 bp including three introns was amplified. This strongly suggests that the origin of HdEG66 is not from symbiotic bacteria but abalone itself.     

Protein carboxyl methyltransferase selectively modifies an atypical form of calmodulin. Evidence for methylation at deamidated asparagine residues

Prolonged incubation of native bovine brain calmodulin with S-adenosyl-L-[methyl-3H]methionine and protein carboxyl methyltransferase results in maximal methylation of only 1-2% of the calmodulin molecules. In contrast, calmodulin which has been subjected to a prior alkaline treatment (0.1 M NH4OH, 37 degrees C for 3 h) can be methylated to a level of 30-50%. This treatment is known to be effective in deamidating certain asparagine residues which lie in unstable sequences, particularly -Asn-Gly- sequences. Bovine brain calmodulin has three such sequences (Watterson, D. M., Sharief, F., and Vanaman, T. C. (1980) J. Biol. Chem. 255, 962-975). The enhancement of methylation by alkaline treatment is substantially reduced if calmodulin is first reacted with bis-(I,I-trifluoroacetoxy)iodobenzene, a reagent which converts the carboxamide group of asparagine and glutamine residues to the corresponding primary amines. Thus, protein carboxyl methyltransferase selectively modifies an abnormal form of calmodulin that is probably deamidated. These findings suggest that protein carboxyl methylation may play a role in the disposition of abnormal proteins which contain atypical, isomerized aspartyl residues arising via spontaneous deamidation of unstable asparagines.     

两种色型黄粉虫酚氧化酶原的cDNA克隆、生物信息学分析及表达水平检测

酚氧化酶是黑色素合成和昆虫免疫的关键酶, 通常以无活性的酚氧化酶原形式存在。为给黄粉虫Tenebrio molitor遗传分化和免疫防御研究提供参考, 本研究采用PCR和RACE技术克隆了黄、 黑两种色型黄粉虫幼虫的酚氧化酶原基因Tm-ppo, 对其cDNA序列及其推导的氨基酸序列进行生物信息学分析, 采用实时荧光定量PCR检测其在两种色型黄粉虫不同发育阶段mRNA表达水平上的动态变化。结果表明： 从黄、 黑两种色型黄粉虫幼虫中克隆出的两个Tm-ppo cDNA序列全长均为2 199 bp, 碱基序列一致性为99%, 包含一个2 055 bp的开放阅读框, 编码684个氨基酸, 它们的编码蛋白有3个氨基酸差异： 第176位（P→A）、 256位（V→A）和648位（I→M）。这两个基因分别被命名为Tm-ppo-1和Tm-ppo-2 （GenBank登录号分别为JX987235和JX987234）。 Tm-ppo-1和Tm-ppo-2编码的酚氧化酶原异构体蛋白（分别为Tm-PPO-1和Tm-PPO-2）存在一个可能的酚氧化酶原水解活化位点（R50~F51残基之间）和一个双铜结合中心（第196~239位残基和第344~411位残基）; 同时含有一个类似巯基酯区域的序列（第579~588位残基）及一个C 末端保守基序（第634~645位残基）; 但它们无氨基端疏水信号肽序列, 也不存在跨膜区域。Tm-PPO-1和Tm-PPO-2的二级结构由大量的α 螺旋、 β-折叠和无规则卷曲组成; 三级结构分为前导域（第16~66位残基）、 不相邻的功能域Ⅰ（第3~15位残基和第67~181位残基）、 功能域Ⅱ（第182~419位残基）和功能域Ⅲ（第420~679位残基）4部分。此外, Tm-ppo-1和Tm-ppo-2在黄、 黑两种色型黄粉虫的各发育期均有表达, 并且不同发育阶段的mRNA表达水平呈现明显的变化规律： 幼虫期﹥成虫期﹥蛹期。同时, 环境温度对Tm-ppo-1和Tm-ppo-2的mRNA表达具有显著影响： 与常温对照组（25~30℃）相比, 42℃暴露24 h和48 h的两种色型黄粉虫幼虫、 蛹和成虫的mRNA表达量明显下调。相同试验条件下, 黑色型黄粉虫幼虫和成虫的Tm-ppo-2 mRNA表达量明显高于黄色型幼虫和成虫的Tm-ppo-1 mRNA表达量, 但两种色型黄粉虫蛹的Tm-ppo异构体表达量无显著差异。本研究为进一步探讨黄粉虫的遗传分化和免疫防御提供了有益参考。     

Complete amino-acid sequence and carbohydrate content of the naturally occurring glucosylceramide activator protein (A1 activator) absent from a new human Gaucher disease variant

Two naturally occurring non-enzymic glucosylceramide activator proteins (A1a and A1b activator) shown previously to be immunochemically not detectable in a new variant of human Gaucher disease (glucosylceramide lipidosis) without glucosylceramidase deficiency, were characterized by amino-acid sequence and carbohydrate content. The complete amino-acid sequence of the A1a activator was determined. The protein consists of 80 amino-acid residues including three disulfide bridges lacking arginine and tryptophan. The molecular mass is 8.95 kDa. About 20% of the polypeptide chain are shorter by two amino-acid residues at the N-terminal end. The A1b activator was characterized by the amino-acid compositions of all tryptic peptides and of the entire protein; sequencing was performed of the regions 1-34 and 42-56. Identical results were obtained for the polypeptide chains of both A1 activators. This suggests that they do not differ in their primary structures which is in agreement with the immunochemical results. The difference between A1a and A1b activator is due to the carbohydrate part. The total amount of 49% carbohydrate in A1a and 76.7% in A1b consists mainly of hexoses. Both chains contain two moles of N-acetylglucosamine per mole protein bound to asparagine in position 22. A comparison of the primary structure of the A1 activator with the sulfatide activator sequence revealed an interesting similarity, especially of the cysteine residues and the carbohydrate-binding asparagine. Sequence homology was also found between a part of the A1 activator sequence and the hemagglutinin neuraminidase of influenza virus as well as to a hypothetical glycoprotein of the Epstein-Barr virus. The comparison with human lysosomal glucosylcerebrosidase showed no sequence similarity.     

Amino-acid Sequence of Human Placental Lactogen

AN earlier report from this laboratory¹ described striking homologies in the amino-acid composition of the peptides obtained from trypsin cleavage of human placental lactogen (HPL) and human growth hormone (HGH) and established a firm biochemical basis for the similarities in biological and immunological activity of the two hormones. The intrachain disulphide bonds were placed in similar locations and the carboxyl-terminal amino-acid sequences were shown to be identical except for one out of fourteen residues². In other studies^3,4, the amino-terminal sequence was determined and noted to be homologous for eleven of the first seventeen residues. We now report the complete amino-acid sequence of HPL and a comparison with the revised structure for HGH recently reported⁴. These two protein hormones are strikingly similar in structure, being identical in 85% of the corresponding positions. Of twenty-eight amino-acid substitutions, twenty-five are favoured changes and all but two of the twenty-five can be explained in terms of a single base change in the triplet codon⁵.