Elsevier

Experimental Eye Research

Volume 65, Issue 6, December 1997, Pages 835-840
Experimental Eye Research

Regular article
Molecular Evidence for the Involvement of Alpha Crystallin in the Colouration/Crosslinking of Crystallins in Age-related Nuclear Cataract

https://doi.org/10.1006/exer.1997.0393Get rights and content

Abstract

The proteins of the lens which become insoluble, crosslinked and coloured as a result of the onset of human nuclear cataract have been studied using a combination of enzymatic digestion and HPLC/mass spectrometry (MS). The objective was to determine if such an approach could provide information on the identities of the polypeptide components involved in the colouration and crosslinking and to discover whether any crystallins predominate in this characteristic post-translational modification process.

Initially, coloured high molecular weight peptides were isolated from a tryptic/chymotryptic digest of the 6mguanidine hydrochloride-insoluble lens protein fraction. These tryptic/chymotryptic peptides were then incubated with pronase and the small peptides released, purified by gel filtration. All but one of the peptides analysed by HPLC/MS/MS were found to contain proline.

Peptides derived from α-crystallin were found to comprise the great majority of the peptides characterised. No γ-crystallin peptides were observed. Both αA-crystallin and αB-crystallin were represented. Further, all but one of these peptides were derived from theN-terminal region of the α-crystallin subunits: a region recently implicated in the chaperone activity of α-crystallin. This finding suggests that the putativeN-terminal domain of α-crystallin may be involved at the molecular level in the process of crosslinking and colouration which is known to be characteristic of age-related nuclear cataract. It is, therefore, conceivable that an early stage of these cataractous modifications may involve α-crystallin acting as a molecular chaperone.

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    Davson, H.

    f1

    Address for correspondence: Roger J. W. Truscott, Australian Cataract Research Foundation, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia.

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