The polypeptide composition of bovine epidermal α-keratin

Abstract

1. The polypedtide chains that comprise the subunits of the tonofilaments, or th alpha-keratin component, of bovine epidermis were fractionated by combination of chromatography on DEAE-cellulose and preparative polyacrylamide-gel electrophoresis. 2. The seve polypeptide chains investigated had generalyy similar properties; all contained two residues per molecule of tryptophan and N-acetylserine was the common N-terminal amino acid residue. 3. On the basis of close similarities in alpha-helix content and amino acid composition, the polypeptide chains were classified into three distinct groups. Each group contained approximately one-third of the total polypeptides on a molar basis. The groups and designated polypeptides chain numbers were: group one, polypeptides 1a and 1b, which had moleculae weights of 58,000, contained about 25% alpha-helix, 86 glutamic acid and 8 cysteine residues per molecule, but which differed in net charge, extinction coefficients and tyrosine contents; group two, polypeptides 2, 3, and 4, which hadmolecular weights within thewithin the range of 52,00-56,000, contained about 48% alpha-helix, 54 glutamic acid and 6 cysteine residues per molecule, but which differed in extinction coefficients and tryosine contents; and group, polypeptides 5 and 6, which had molecular weights of 47000-48000, contained about 56% alpha-helix, 64 glutamic acid and 4 cysteine residues per molecule, but which differed in extinction coefficients and tyrosine contents...

Microfibrillar Proteins of Wool: Partial Specific Volumes and Molecular Weights in Denaturing Solvents

“…The IX-helical contents of components 5, 7 and 8 are 25 %, 45 % and 56 % respectively (Crewther et al 1968; Dowling unpublished data) and these are also similar to the values found for the three groups of polypeptide chains from bovine epidermal IX-keratin (Steinert and Idler 1975).…”

“…The range of molecular weights (45000-60000) found for the polypeptide chains of the wool microfibril is comparable to that found for the IX-keratin from the filaments of bovine epidermis (Skerrow 1974;Lee and Baden 1976;Steinert and Idler 1975).…”

“…If the standard proteins and unknowns bind the same amount of SDS and carry the same charge they should share a common intercept, Yo, which is related to the net charge. This has been shown for some systems (Frank and Rodbard 1975;Steinert and Idler 1975) but in other cases (Banker and Cotman 1972) a positive correlation is found between Yo and KR • Fig. 4 shows the relation between Yo and KR obtained in the present investigation where it is seen that the free mobility is related to molecular size as found by Banker and Cotman (1972).…”

“…Many factors affect the order of migration of proteins in SDS gel electrophoresis and hence derived molecular weights. Factors shown to affect migration are: chemical modification-for example, esterification (McCumber and Clem 1976), maleylation (Banker and Cotman 1972), method of modification of sulfhydryl groups (Takagi et al 1975); conditions of electrophoresis (Capaldi et al 1977) and freeze-drying of proteins (Steinert and Idler 1975). More recently de Jong et al (1978) have shown that a single amino acid substitution influenced the mobility of closely related proteins.…”

Identification of mouse mammary epithelial cells by immunofluorescence with rabbit and guinea pig antikeratin antisera.

“…These quantitative differences in the keratin content of the myoepithelial cells versus that in the other mammary epithelial cells, (ii) differences in keratin composition between species (mouse versus human) and between tissues (mammary gland versus epidermis), and (iii) recognition of different antigenic sites in the keratin polypeptides by the immune systems of the rabbit and guinea pig. Keratins from several species have been studied and shown to consist of multiple numbers of subunit polypeptides (3,(19)(20)(21). Differences in keratin composition are known to occur during the course of differentiation of epidermal cells (22)(23)(24), among different epidermal (21,25) and stratified squamous (26) epithelial cells of the same organism, and between fetal and adult tissues (27).…”