Biomedical subjects

M C Wilce

Publications and source records attributed to M C Wilce.

22 records · Page 2Linked to original sources

PubMed1993

Conformational states of human placental glutathione transferase as probed by limited proteolysis.

Limited proteolysis experiments have been carried out on human placental glutathione transferase in its different forms. The reduced enzyme, as well as the oxidized form and that inactivated with cystamine were all sensitive to 10% (w/w) trypsin, under nondenaturing conditions. The proteolytic cleavage was accompanied by a concomitant loss of enzymatic activity. On the contrary, the presence of glutathione or glutathione conjugates strongly protected the reduced enzyme against inactivation and from the proteolytic attack. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis and peptide sequence analysis showed that only the peptide bond between Lys 44 and Ala 45 was cleaved. Since Lys 44 has been demonstrated to be involved in the glutathione binding, it is suggested that the region surrounding this amino acid residue (alpha B helix) could be more exposed to the solvent, in the absence of glutathione. Crystallographic data also indicated that this region is flexible, supporting the idea that it may be involved in the observed conformational change upon glutathione binding.

Alanine↗

PubMed1993

X-ray diffraction studies of fibrils formed from peptide fragments of transthyretin.

Two synthetic peptide fragments of the plasma protein transthyretin (TTR), previously shown to form fibrillar structures in vitro, have been examined using electron microscopy and X-ray diffraction. The fibrils displayed all characteristics of cross beta-sheet conformation with antiparallel strand spacing of 4.7 A and intersheet spacings of 8-10 A as well as reflections indicating further lateral repeating units. A third peptide containing a substitution equivalent to a mutation in TTR known to increase the propensity of TTR to form amyloid was also examined. It also formed fibrils and showed similar cross beta-sheet structure, but with closer intersheet packing than its native equivalent.

Amino Acid Sequence↗

PubMed1993

High-performance liquid chromatography of amino acids, peptides and proteins. CXXII. Application of experimentally derived retention coefficients to the prediction of peptide retention times: studies with myohemerythrin.

Amino acid retention coefficients were derived from the experimental retention data of 118 overlapping peptide heptamers related to the primary amino acid sequence of myohemerythrin. Individual retention coefficient values for each amino acid were derived by a multiple linear regression matrix approach. Retention data were derived for five different experimental conditions including different organic modifiers (acetonitrile, methanol or 2-propanol), different mobile phase additives (trifluoroacetic acid or potassium phosphate) and different silica-based stationary phase ligands (octadecyl or phenyl groups). A high degree of correlation was observed between these experimentally derived amino acid coefficients (EXP) and the coefficients (LIT) which we recently reported derived from the retention data of over 2000 peptides [M. C. J. Wilce et al., J. Chromatogr., 536 (1991) 165 and 548 (1991) 105]. These results demonstrated that the LIT and EXP coefficients can be used for the prediction of the retention of any peptide set. The effect of peptide length was also further investigated and the correlation results demonstrated the importance of peptide flexibility on the final value of the amino acid coefficient.

Amino Acid Sequence↗

PubMed1991

Duchenne muscular dystrophy and dystrophin: sequence homology observations.

Duchenne muscular dystrophy (DMD) is a genetically transmitted disease characterized by progressive muscle weakness and usually leads to death. DMD results from the absence, deficiency or dysfunction of the protein dystrophin. Analysis of protein data bases, including homology alignments and domain recognition patterns, have located highly significant correlations between dystrophin and other calcium regulating proteins. In particular, a major portion of the dystrophin sequence has been found to contain repeating units of approximately 100 amino acid residues. These repeating units were found to exhibit significant homology to troponin I. Troponin I has been found to bind to the calcium binding proteins calmodulin and troponin C. The regions of highest homology were characterized by patterns of high localization of charged amino acids and thus could represent a possible calmodulin or troponin C surface accessible binding site. Since subcellular localization studies have indicated that dystrophin is associated with the triadic junction, these findings imply that dystrophin could be involved in controlling intracellular calcium homeostasis.

Amino Acid Sequence↗