Type II intermediate-filament proteins from wool. The amino acid sequence of component 5 and comparison with component 7c

Abstract

Component 5 is one of the four type II intermediate-filament proteins found in the hard keratin wool. It was isolated as the S-carboxymethyl derivative from Merino wool and its amino acid sequence was determined by manual and automatic sequencing of peptides produced by chemical and enzymic cleavage. Component 5 is an N-terminally blocked molecule of 503 residues and Mr (not including the blocking group) of 56,600. The blocking group has not been identified. The amino acid sequence of component 5 shows 77% sequence identity with that of component 7c, another type II wool intermediate-filament protein [Sparrow, Robinson, McMahon & Rubira (1989) Biochem. J. 261, 1015-1022]. The sequence similarity extends from the N-termini of the two molecules to residue 459 (component 5 sequence); however, there is no recognizable sequence similarity in the remaining C-terminal 43 amino acid residues. Details of procedures used in determining the sequence of component 5 have been deposited as a Supplementary Publication SUP 50168 (80 pages) at the British Library Document Supply Centre, Boston Spa, Wetherby, West Yorkshire, LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1992) 281, 5. The information comprises: (1) details of chemical and enzymic methods used for cleavage of component 5, peptide CN1, the peptide mixture CN2/3 and various other peptides, (2) details of the procedures used for the fractionation and purification of peptides from (1), including Figures showing the elution profiles from the chromatographic steps used, and (3) details of the method used to determine the C-terminal sequence of component 5.