The primary structure of component 8c-1, a subunit protein of intermediate filaments in wool keratin. Relationships with proteins from other intermediate filaments

Abstract

Component 8c-1, one of four highly homologous component-8 subunit proteins present in the microfibrils of wool, was isolated as its S-carboxymethyl derivative and its amino acid sequence was determined. Large peptides were isolated after cleaving the protein chemically or enzymically and the sequence of each was determined with an automatic Sequenator. The peptides were ordered by sequence overlaps and, in some instances, by homology with known sequences from other component-8 subunits. The C-terminal residues were identified by three procedures. Full details of the various procedures used have been deposited as Supplementary Publication SUP 50133 (4 pp.) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1986) 233, 5. The result showed that the protein comprises 412 residues and has an Mr, including the N-terminal acetyl group, of 48,300. The sequence of residues 98-200 of component 8c-1 was found to correspond to the partial or complete sequences of four homologous type I helical segments previously isolated from helical fragments recovered from chymotryptic digests of microfibrillar proteins of wool [Crewther & Dowling (1971) Appl. Polym. Symp. 18, 1-20; Crewther, Gough, Inglis & McKern (1978) Text. Res. J. 48, 160-162; Gough, Inglis & Crewther (1978) Biochem. J. 173, 385]. Considered in relation to amino acid sequences of other intermediate-filament proteins, the sequence is in accord with the view that keratin filament proteins are of two types [Hanukoglu & Fuchs (1983) Cell (Cambridge, Mass.) 33, 915-924]. Filament proteins from non-keratinous tissues, such as desmin, vimentin, neurofilament proteins and the glial fibrillary acidic protein, which form monocomponent filaments, constitute a third type. It is suggested that as a whole the proteins from intermediate filaments be classed as filamentins, the three types at present identified forming subgroups of this class. The significant homologies between types I, II and III occur almost exclusively in segments of the chain that have been identified as having a coiled-coil structure together with the relatively short sections connecting these segments. The non-coiled-coil segments at the C- and N-termini show no significant homology between types, nor is homology in these segments apparent in all members of one type. Component 8c-1 does not show homology in its terminal segments with the known sequence of any other filamentin.(ABSTRACT TRUNCATED AT 400 WORDS)

A Role for the 1A and L1 Rod Domain Segments in Head Domain Organization and Function of Intermediate Filaments: Structural Analysis of Trichocyte Keratin

“…The primary structures of Type I and Type II trichocyte keratins were collected from various databases (see, for example, Bertolino et al, 1988Bertolino et al, , 1990Dowling et al, 1986;Wilson et al, 1988;Yu et al, 1991Yu et al, , 1993Winter et al, 1994;Tobiasch et al, 1992;Powell et al, 1992Powell et al, , 1993Sparrow et al, 1989Sparrow et al, , 1992Powell and Beltrame, 1994;Fink et al, 1995;Bowden et al, 1997;Powell and Rogers, 1997;Rogers et al, 1995Rogers et al, , 1996Rogers et al, , 1997Rogers et al, , 1998. The N-terminal head domain sequences were then compared (within a single type) to determine the similarities and differences that existed and hence ascertain the consensus structures (Fig.…”

“…In modeling the 1A segment the sequences for sheep Type I 8c-1 (Dowling et al, 1986, Wilson et al, 1988 and sheep Type II 7c (Sparrow et al, 1989) were used. The initial structures for the 1A coiled-coil segment, extended ␤-chain, and four-stranded antiparallel ␤-sheet were each built separately based on similar structures found in proteins in the Brookhaven Protein Data Bank (Bernstein et al, 1977).…”

A new look into an old problem: keratins as tools to investigate determination, morphogenesis, and differentiation in skin.

“…6H), but not in any of the samples of skin from 17 to 20 days of gestation (lanes 17-20). This band corresponds to the predicted molecular size of the type I hair-specific keratin mRNAs (Dowling et al 1986). Collectively, our immunoblot and Northern blot analyses suggest that the major appearance of hair-specific keratins and their mRNAs occurs after embryogenesis in the rat.…”

The proteomics of keratin proteins

“…A similar situation exists for the Type II IFPs, where only three full sequences are available [2,[18][19][20][21][22]. However at least two new sequences, oHa5 and oHa8 (Table 1) have been uncovered [23], which have strong homology to human hair proteins.…”