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Biosynthesis and characterization of the isoelectric variants of prekeratin polypeptides from human epidermis [Abstract]

Bowden, Paul Edward, Bladon, P. T., Wood, E. J. and Cunliffe, W. J. 1982. Biosynthesis and characterization of the isoelectric variants of prekeratin polypeptides from human epidermis [Abstract]. British Journal of Dermatology 106 (6) , p. 726. 10.1111/j.1365-2133.1982.tb14713.x

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The synthesis of the tonofilament protein, prekeratin, is a major event during the terminal differentiation of human epidermis and modification of this protein gives rise to mature keratin filaments, a major component of the corneocyte. In addition to size heterogeneity, we have recently demonstrated that considerable charge heterogeneity exists amongst the prekeratin polypeptides. In this commimication we have examined the biosynthesis of these isoelectric variants and demonstrated that many of them are phosphorylated prekeratin polypeptides. Scalp epidermis was incubated at 37°C for 5 h in Eagle's MEM containing labelled amino acids ('*C-serine, '*C-glycine or ^'S-methionine) or ^^P orthophosphate. Labelled prekeratin was extracted and purified and analysed by gradient slab SDS-PAGE, two dimensional electrophoresis and fiuorography. Scalp prekeratin has five major polypeptides (mol. wt 70,000, 60,000, 57,000, 52,000 and 46,000), the two larger chains having neutral isoelectric variants (pH 64-78) and the smaller chains having acidic isoelectric variants (pH 52-57). Typically the yield of prekeratin was 25 mg/g epidermis which was labelled to high specific activity (io'-io* c.p.m./mg). Glycine was incorporated into the isoelectric variants of the 70,000 and 57,000 polypeptides while serine also labelled the 60,000 and 52,000 polypeptides. Methionine labelled all five polypeptides but phosphate labelled only the four larger chains and only the more acidic of the isoelectric variants. It is therefore concluded that much of the isoelectric variation is due to phosphorylation of four nascent prekeratin polypeptides and that the smallest polypeptide (46,000) is probably Beta-actin.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Medicine
Subjects: R Medicine > R Medicine (General)
R Medicine > RL Dermatology
Additional Information: Society Proceedings - BAD Investigative Group Meeting, Bristol, January 1982. Summaries of papers.
Publisher: Wiley-Blackwell
ISSN: 0007-0963
Last Modified: 12 Jun 2019 02:24

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