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Biomedical subjects

C Gerard

Publications and source records attributed to C Gerard.

154 records · Page 9Linked to original sources
PubMed1980

The amino acid sequence specificity of a protease from spores of Bacillus megaterium.

Previous work has shown that the degradation of 20% of total protein which occurs early in germination of Bacillus megaterium spores is initiated by an endoprotease. This enzyme is found only in the spore and is active only on the spore proteins degraded during germination. Action of the spore protease in vitro on the three major proteins (Proteins A, B, and C) which are degraded in vivo during germination results in cleavage of one (A and C protein) or two (B protein) peptide bonds. The sequences surrounding the cleavage sites are -Tyr-Glu- Ile-Ala-Ser-Glu-Phe- in the A protein, -Phe-Glu- Ile-Ala-Ser-Glu-Phe- in the C protein, and -Thr-Glu- Phe-Gly-Ser-Glu-Thr-, and -Thr-Glu- Phe-Ala-Ser-Glu-Thr- in the B protein, with cleavage taking place at the glutamyl bond noted by the arrow. The similarity of these four sequences suggests the possibility that the specificity of the spore protease may be due to its requirement for a specific pentapeptide sequence of the type -R-Glu-(Phe or Ile)-(Gly or Ala)-Ser-Glu-R- for recognition and cleavage. However, it is also possible that it is the conformation of the A, B, and C proteins which determines their site of cleavage by the spore protease.

Amino Acid Sequence↗
PubMed1977

Covalent structure of the membranous segment of horse cytochrome b5. Chemical cleavage of the native hemoprotein.

The complete covalent structure of the membranous segment of horse liver cytochrome b5 has been determined. This peptide spans residues 91 to 133 of the cytochrome molecule, and contains the segment responsible for the association of the hemoprotein with microsomal or synthetic vesicles. Two peptides, residues 91 to 127 and 128 to 133, comprising the entire membranous moiety were isolated from a tryptic digest of urea-denatured apoprotein. The membranous segment (residues 91 to 127) could be separated from all other tryptic peptides by a single gel filtration step. Trypsin digestion of succinylated cytochrome produced similar peptides, residues 89 to 127 and 128 to 133. The covalent structures for residues 89 to 127 and 128 to 133 were derived from automated sequenator analysis of tryptic peptides. Chemical cleavage at tryptophanyl, or methionyl residues, or both, by the method of Ozols and Gerard ((1977) J. Biol. Chem. 252, 5986-5989) provided the overlapping peptides from which the following unique sequence was deduced: (formula: see text).

Amino Acid Sequence↗
PubMed1977

Cleavage of tryptophanyl peptide bonds in cytochrome b5 by cyanogen bromide.

Quantitative cleavage of peptide bonds adjacent to tryptophanyl and methionyl residues in the polar moiety of cytochrome b5 was effected using cyanogen bromide in the presence of heptafluorobutyric and formic acids. Application of this method to native cytochrome b5 resulted in cleavage at tryptophanyl and methionyl residues in the polar and membranous segments in high yield. Amino acid analysis of peptides isolated from such digests indicated that tyrosine was modified and the derivative eluted in a position preceding lysine; however, the color constant with ninhydrin remained unchanged. Hydriodic acid hydrolysis of the phenylthiohydantoin derivative of the modified tyrosine regenerated the parent amino acid. Peptides containing the altered tyrosine remained susceptible to chymotryptic cleavage at this residue. Cleavage of methionyl bonds could be prevented by methylene blue-sensitized photooxidation prior to cyanogen bromide/anhydrous heptafluorobutyric acid treatment. The conditions employed for photooxidation were selective for methionyl residues, and the yield and specificity of tryptophanyl cleavage by the cyanogen bromide/anhydrous heptafluorobutyric acid method was unaffected.

Amino Acid Sequence↗
PubMed1977

Primary structure of the membranous segment of cytochrome b5.

The primary structure of the membranous segment of porcine liver microsomal cytochrome b5 has been determined. This polypeptide is at the COOH terminus of the cytochrome molecule and consists of 43 amino acids. It is essential for the insertion of the cytochrome into the endoplasmic reticular membrane. Automated sequence analysis of tryptic and cyanogen bromide/anhydrous heptafluorobutyric acid peptides provided data from which the following unique amino acid sequence was deduced: Ile-Ala-Lys-Pro-Ser-Glu-Thr-Leu-Ile-Thr-Thr-Val-Glu-Ser-Asn-Ser-Ser-Trp-Trp-Thr-Asn-Trp-Val-Ile-Pro-Ala-Ile-Ser-Ala-Leu-Val-Val-Ser-Leu-Met-Tyr-His-Phe-Tyr-Thr-Ser-Glu-Asn. A prediction of alpha-helices, beta-structures, and beta-turns basedon the sequence of this polypeptide is also presented.

Amino Acid Sequence↗
PubMed1976

Proteolytic cleavage of horse liver cytochrome b5. Primary structure of the heme-containing moiety.

The amino acid sequence of the NH2-terminal segment of horse cytochrome b5, containing the heme binding site, has been determined. A fragment, representing residues 7 through 90, was obtained by tryptic cleavage of native cytochrome b5. Chymotryptic cleavage of native cytochrome b5 yields a peptide containing residues 1 through 98. Contrary to native cytochrome b5, neither derivative showed binding to horse liver microsomal vesicles. The complete primary structure of the polar moiety has been deducted from automated and manual sequence analysis of peptides obtained from tryptic and chymotryptic digests of native cytochrome and apocytochrome preparations. Glutamyl residues at positions 41, 42, 47, and 48 appear to be replaced by aspartyl residues in some molecules. Such microheterogeneity is not observed at glutamyl residues at other positions. The native cytochrome b5 preparation contains a blocked NH2-terminal residue.

Amino Acid Sequence↗
PubMedDate not supplied

A new paradigm of T cell allergy: requirement for the B-1 cell subset.

BACKGROUND: We have uncovered a role for B-1-B-cell-produced IgM antibody, in the initiation of contact sensitivity (CS) in mice. CS and delayed-type hypersensitivity (DTH) involve recruitment of T cells to the tissues, to be activated by antigen-presenting cells (APC), and then make cytokines. Little is known about low recruitment is initiated. In CS, soon after immunization, the unique B-1 cell subset, responsible for the formation of most IgM, is activated to produce antigen (Ag)-specific IgM for export to tissues. IgM forms complexes with challenge Ag, activating the classical complement (C) pathway, generating C5a, to activate endothelium directly, or indirectly via C5a receptors (R) on mast cells and platelets, that release vasoactive amines (serotonin) and cytokines (TNF-alpha). These act together to induce vasodilatation, vascular permeability and expression of endothelial adhesion molecules to promote optimal T cell recruitment. METHODS AND RESULTS: New findings that established this pathway include: (1) absent CS response in C-deficient, or C-inhibited mice; (2) local generation of C5a in CS tissue extracts; (3) absent CS in C5aR-/- mice; (4) decreased CS in B cell and B-1-cell-deficient mice, and (5) reconstitution of CS by transfer of B-1 cells, or hapten-specific IgM. CONCLUSION: These findings indicate that the B-1 subset producing Ag-specific IgM is required early in CS to activate C, to induce vasoactive mediators that initiate local T recruitment.

Animals↗