Problems Associated with the Identification of Proteins in Homologous Families: The Wool Keratin Family as a Case Study

✍ Scribed by Jeffrey E. Plowman; Warren G. Bryson; Leanne M. Flanagan; T.William Jordan

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 373 KB
• Volume: 300
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1006/abio.2001.5459

✦ Synopsis

The keratin proteins from wool can be divided into two classes: the intermediate filament proteins (IFPs) and the matrix proteins. Using peptide mass spectral fingerprinting it was possible to match spots to the known theoretical sequences of some IFPs in webbased databases, as enzyme digestion generated sufficient numbers of peptides from each spot to achieve this. In contrast, it was more difficult to obtain good matches for some of the lower molecular weight matrix proteins. Relatively few peaks were generated from tryptic digests of high-sulfur proteins because of their lower molecular weight and the absence of basic residues in the first two-thirds of the sequence. Their high sequence homology also means that generally only a few of these peptides could be considered to be unique identifiers for each protein. Nevertheless, it was still possible to uniquely identify some of these proteins, while the presence of two peptides in the matrix-assisted laser desorption/ionization time-offlight mass spectrum allowed classification of other protein spots as being members of this family. Only one major peptide peak was generated by the highglycine tyrosine proteins (HGTPs) and there were relatively few sequences available in web-based databases, limiting their identification to one HGTP family.