Selective cleavage of the connector segments within the myosin-S1 heavy chain by staphylococcal protease

The existence of the two connector segments linking the tryptic 50 kDa fragment of skeletal S1 heavy chain to the adjacent 27 kDa and 20 kDa peptides was ascertained by digestion of S1 with staphylococcal protease which was found to act specifically at these particular regions. Three new peptides of Mr 28000, 48000 and 22000 were produced and the novel S1 derivative formed had an intact actin-activated ATPase activity. Amino acid sequence analyses indicated that the 48 kDa and 22 kDa peptides overlap the two connector elements.     

MAP1B is encoded as a polyprotein that is processed to form a complex N-terminal microtubule-binding domain.

Microtubule-associated protein 1B (MAP1B), an abundant developmentally regulated neuronal protein, is a stoichiometric complex of a heavy chain and two light chains (light chain 1 and light chain 3). We find that light chain 1 is encoded within the 3' end of a previously reported MAP1B heavy chain cDNA. Amino acid sequencing, epitope mapping, Northern blotting, and Southern blotting indicate that the light chain and heavy chain are encoded by the same mRNA within the same open reading frame. In addition, amino acid sequencing of a 120 kd microtubule-binding and light chain-binding fragment of the heavy chain reveals that light chain 1 binds near the heavy chain N-terminus. Together these data indicate that the heavy chain and light chain 1 are produced by proteolytic processing of a MAP1B polyprotein and form a complex microtubule-binding domain.     

Identification of the serine residue phosphorylated by protein kinase C in vertebrate nonmuscle myosin heavy chains

Two-dimensional mapping of the tryptic phosphopeptides generated following in vitro protein kinase C phosphorylation of the myosin heavy chain isolated from human platelets and chicken intestinal epithelial cells shows a single radioactive peptide. These peptides were found to comigrate, suggesting that they were identical, and amino acid sequence analysis of the human platelet tryptic peptide yielded the sequence -Glu-Val-Ser-Ser(PO4)-Leu-Lys-. Inspection of the amino acid sequence for the chicken intestinal epithelial cell myosin heavy chain (196 kDa) derived from cDNA cloning showed that this peptide was identical with a tryptic peptide present near the carboxyl terminal of the predicted alpha-helix of the myosin rod. Although other vertebrate nonmuscle myosin heavy chains retain neighboring amino acid sequences as well as the serine residue phosphorylated by protein kinase C, this residue is notably absent in all vertebrate smooth muscle myosin heavy chains (both 204 and 200 kDa) sequenced to date.     

Expression of two methionine-rich storage protein genes of Plutella xylostella (L.) in response to development, juvenile hormone-analog and pyrethroid

We cloned and characterized cDNA of two storage protein (SP) genes, PxSP1 and PxSP2, from the diamondback moth, Plutella xylostella (Lepidoptera: Yponomeutidae) and investigated their expression. PxSP1 and PxSP2 each encoded a putative protein of 91 kDa. Nucleotide and deduced amino acid identities between the two genes were 79% and 82%, respectively. Amino acid composition (methionine>4%), sequence homology with other insect storage proteins and the phylogenetic analysis suggested that the genes belong to the subfamily of moderately methionine-rich SP genes. The genes were predominantly expressed in the last instar female larvae and the mRNA levels were suppressed by treatment with a juvenile hormone-analog. Treatment of female larvae with sublethal dose of a pyrethroid caused a significant increase in mRNA levels of both genes. Induction of PxSP1 and PxSP2 genes as a result of pyrethroid application may have implications with respect to reproduction as methionine-rich proteins are known as a key element for egg production.     

Biochemical and molecular characterization and expression of the 11S-type storage protein from Coffea arabica endosperm

In order to define better the endosperm protein content of commercial coffee species Coffea arabica (Arabica) and C. canephora (Robusta), the principal storage protein of coffee grains has been analysed by 2-dimensional electrophoresis (2DE) and amino acid microsequencing. The most abundant polypeptide spots observed on mature coffee grain 2DE profiles were found to be subunits of the same protein, which exists as multiple isoforms with varying pIs. Strong sequence similaritywas found to the 11S family of plant storage proteins. The structure is typical of the 11S type, which occurs as a precursor of 55 kDa, and is observed under denaturing and reducing conditions on 2DE profiles in the form of cleavage products at approximately 20 kDa (β arms) and 32 kDa (α arms). Differences between Arabica and Robusta 2DE profiles indicate a secondary 11S protein family in some varieties of the latter. The existence of multiple pI forms may indicate that a multigene family encodes for these proteins. We estimate that the protein accounts for approximately 45 % of total grain protein. A cloned full-length cDNA of 1 706 bp coding for one of the isoforms is described and discussed in relation to other coffee storage protein sequences.     

Differential expression of a gene for a methionine-rich storage protein in maize

Summary A methionine-rich 10 kDa zein storage protein from maize was isolated and the sequence of the N-terminal 30 amino acids was determined. Based on the amino acid sequence, two mixed oligonucleotides were synthesized and used to probe a maize endosperm cDNA library. A fulllength cDNA clone encoding the 10 kDa zein was isolated by this procedure. The nucleotide sequence of the cDNA clone predicts a polypeptide of 129 amino acids, preceded by a signal peptide of 21 amino acids. The predicted polypeptide is unique in its extremely high content of methionine (22.5%). The maize inbred line BSSS-53, which has increased seed methionine due to overproduction of this protein, was compared to W23, a standard inbred line. Northern blot analysis showed that the relative RNA levels for the 10 kDa zein were enhanced in developing seeds of BSSS-53, providing a molecular basis for the overproduction of the protein. Southern blot analysis indicated that there are one or two 10 kDa zein genes in the maize genome.     

Characterization of a spinach psbS cDNA encoding the 22 kDa protein of photosystem II.

An intrinsic 22 kDa polypeptide is found associated with the oxygen-evolving photosystem II (PSII) core complex in all green plants and cyanobacteria so far examined, although it does not appear to be required for oxygen evolution. Amino acid sequence information obtained from the purified 22 kDa protein was used to construct a probe that was employed to isolate a full-length cDNA clone encoding the 274-residue precursor of the 22 kDa protein. Hydropathy plot analysis predicts the existence of four membrane-spanning helices in the mature protein. The two halves of the approximately 200-residue mature protein show high sequence similarity to each other, suggesting that the psbS gene arose from an internal gene duplication. The 22 kDa protein has some sequence similarity to chlorophyll a/b-binding proteins.     

Proteolysis of factor Va by factor Xa and activated protein C

Bovine Factor Va, produced by selective proteolytic cleavage of Factor V by thrombin, consists of a heavy chain (D chain) of Mr = 94,000 and a light chain (E chain) of Mr = 74,000. These peptides are noncovalently associated in the presence of divalent metal ion(s). Each chain is susceptible to proteolysis by activated protein C and by Factor Xa. Sodium dodecyl sulfate electrophoretic analysis indicates that cleavage of the E chain by either activated protein C or Factor Xa yields two major fragments: Mr = 30,000 and Mr = 48,000. Amino acid sequence analysis indicates that the Mr = 30,000 fragments have identical NH2-terminal sequences and that this sequence corresponds to that of intact E chain. The Mr = 48,000 fragments also have identical NH2-terminal sequences, indicating that activated protein C and Factor Xa cleave the E chain at the same position. Sodium dodecyl sulfate electrophoretic analysis indicates that activated protein C cleavage of the D chain yields two products: Mr = 70,000 and Mr = 24,000. Amino acid sequence analysis indicates that the Mr = 70,000 fragment has the same NH2-terminal sequence as intact D chain, whereas the Mr = 24,000 fragment does not. Factor Xa cleavage of the D chain also yields two products: Mr = 56,000 and Mr = 45,000. The Mr = 56,000 fragment corresponds to the NH2-terminal end of the D chain and Factor V. Functional studies have shown that both chains of Factor Va may be entirely cleaved to products by Factor Xa without loss of activity, whereas activated protein C cleavage results in loss of activity. Since activated protein C and Factor Xa cleave the E chain at the same position, the cleavage of the D chain by activated protein C is responsible for the inactivation of Factor Va.     

Purification and Properties of Ferritin from the Last Instar Larval Hemolymph of Protaetia brevitarsis (Coleoptera)

Ferritin, an iron storage protein, has been purified from the last larval hemolymph of Protaetia brevitarsis (coleoptera) by KBr density gradient ultracentrifugation and resource Q (anion exchange chromatography) using fast performance liquid chromatography (FPLC) system. The iron content of ferritin was determined by atomic emission spectroscopy and FereneS stain. Ferritin of P. brevitarsis is shown to have two different subunits presented on a SDSPAGE in normal (N) and ironinjected (I) hemolymph. SDS PAGE revealed that the ferritin consists of two major polypeptides of 27 and 28 kDa in normal hemolymph. Interestingly, however, 30 kDa subunit was substituted for 28 kDa when iron was injected into the hemolymph. Apporximate isoelectric points of 27 kDa, 28 kDa, and 30 kDa ferritin subunits were 6.7, 6.75, and 6.8, respectively. Ferritin of P. brevitarsis was detected by FereneS stain and confirmed by Western blotting using its polyclonal antibody. Other characteristics such as amino acid composition and Nterminal amino acid sequence were investigated. Amino acid composition of ferritin (N and I) was rich in alanine, glycine, glutamine or glutamic acid and serine, but poor in histidine, arginine, methionine and phenylalanine.     

Characterization of RNase-like major storage protein from the ginseng root by proteomic approach

The most abundant root proteins of ginseng (Panax ginseng) have been detected and identified by comparative proteome analysis with cultured hairy root of ginseng. Four abundant proteins (28, 26, 21 and 20 kDa) of P. ginseng had isoforms with different pl values on two-dimensional gel electrophoresis (2DE). The results of N-terminal and internal amino acid sequencing, however, showed that all of them originate from a 28 kDa protein, known as ginseng major protein (GMP). The GMP gene was searched for in the expressed sequence tag database of P. ginseng and found to encode a 27.3 kDa protein having 238 amino acid residues. Analysis of the amino acid sequences indicates that GMP exhibits high sequence homology with plant RNases and RNase-like proteins. However, purified GMP had no RNase activity even though it has conserved amino acid residues known to be essential for active sites of RNase. The GMPs present in ginseng main root were not expressed in cultured hairy roots of ginseng. 2DE analysis showed that the amounts of GMPs in main roots change according to seasonal fluctuation. These results suggest that the GMPs are root-specific RNase-like proteins, which function as vegetative storage proteins of ginseng for survival in the natural environment.     

Characterization of the 12S storage protein of Brassica napus (cruciferin): Disulfide bonding between subunits

Cruciferin (12S globulin) is a large, neutral, oligomeric protein synthesized in rapeseed ( Brassica napus ) during the seed development. It is composed of six subunit pairs. Each pair consists of one heavy α chain (30 kDa) and one light β chain (20 kDa). Four different subunit pairs exist. In contrast to earlier studies, our investigations using two-dimensional electrophoresis showed, that the majority of α and β chains of each subunit are disulfide-linked. Analysis of subunit composition of cruciferin hexamers by ion-exchange chromatography suggested that a large array of hexamers exist, composed of mixed combinations of the four subunits.     

Fibroin silk proteins from the nonmulberry silkworm Philosamia ricini are biochemically and immunochemically distinct from those of the mulberry silkworm Bombyx mori

Silk proteins were isolated from the cocoons of the nonmulberry silkworm, Philosamia ricini. Three polypeptides of 97, 66, and 45 kDa were identified. The 66-kDa molecule represented sericin, whereas the 97-kDa and the 45-kDa polypeptides linked together through a disulfide bond constituted the fibroin protein. Antibodies raised against the 97-kDa P. ricini fibroin heavy chain reacted specifically with this molecule and did not recognize fibroin heavy chain from another nonmulberry silkworm, Antheraea assama or from the mulberry silkworm, Bombyx mori, suggesting the presence of P. ricini species-specific determinants in this heavy chain. Antibodies generated against fibroin light chain of P. ricini also showed similar reactivity pattern. Immunoblot analysis with proteins isolated from the silk glands of P. ricini at different stages of larval development showed that the expression of fibroin heavy chain was developmentally and spatially regulated. The protein was most abundant in the 5th instar larva, and could be detected in the middle and the posterior but not the anterior silk glands. The amino acid composition of the 97-kDa fibroin protein showed abundance of glutamic acid and did not contain (Gly-Ala)(n) motifs, a characteristic feature of B. mori fibroin heavy chain. Our study reveals significant differences between the nonmulberry silkworm P. ricini and the mulberry silkworm B. mori in the biochemical composition and immunochemical characteristics of fibroin heavy chain. These differences might be responsible for the differences seen in the quality of silk produced by these two silkworms.     

Botulinum neurotoxin type E fragmented with endoproteinase Lys-C reveals the site trypsin nicks and homology with tetanus neurotoxin

Botulinum neurotoxin type E, a 150 kDa single chain protein, cleaved with endoproteinase Lys-C yielded 113, 73, and 50 kDa fragments. The N-terminal sequence of the 113 kDa fragment, Gly-Ile-Arg-Lys-Ser-Ile-Cys-Ile, overlaps the N-terminal sequence, Lys-Ser-Ile-Cys-Ile, of the 103 kDa heavy chain produced by nicking the neurotoxin with trypsin. The -Arg-Lys- bond is therefore the site on the single chain type E NT where trypsin nicks generating the 50 kDa light and 103 kDa heavy chains of the dichain NT. The sequence of the first 50 N-terminal residues of the 73 kDa fragment were determined. This fragment is a segment of the heavy chain; 50% of the 50 residues are present in identical positions in a similar segment of the heavy chain of tetanus neurotoxin.