An atypical form of αB-crystallin is present in high concentration in some human cataractous lenses

Jimenez-Asensio, Jose ; Colvis, Christine. M ; Kowalak, Jeffrey. A ; Duglas-Tabor, Yvonne ; Datiles, Manuel. B ; Moroni, Maria ; Mura, Umberto ; Mohan Rao, Ch. ; Balasubramanian, Dorairajan ; Janjani, Alireza ; Garland, Donita (1999) An atypical form of αB-crystallin is present in high concentration in some human cataractous lenses Journal of Biological Chemistry, 274 (45). pp. 32287-32294. ISSN 0021-9258

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Two unique polypeptides, 22.4 and 16.4 kDa, were prominent in some human cataracts. Both proteins were identified as modified forms of the small heat shock protein, αB-crystallin. The concentration of total αB-crystallin in most of these cataracts was significantly increased. The 22.4-kDa protein was subsequently designated as αBg. Mass spectrometric analyses of tryptic and Asp-N digests showed αBg is αB-crystallin minus the C-terminal lysine. αBg constituted 10–90% of the total αB-crystallin in these cataracts and was preferentially phosphorylated over the typical form of αB-crystallin. Human αBg and αB-crystallin were cloned and expressed inEscherichia coli. The differences in electrophoretic mobility and the large difference in native pI values suggest some structural differences exist. The chaperone-like activity of recombinant human αBg was comparable to that of recombinant human αB-crystallin in preventing the aggregation of lactalbumin induced by dithiothreitol. The mechanism involved in generating αBg is not known, but a premature termination of the αB-crystallin gene was ruled out by sequencing the polymerase chain reaction products of the last exon for the αB-crystallin gene from lenses containing αBg. The 16.4-kDa protein was an N-terminally truncated fragment of αBg. The high concentration of αB-crystallin in these cataracts is the first observation of this kind in human lenses.

Item Type:Article
Source:Copyright of this article belongs to The American Society for Biochemistry and Molecular Biology.
ID Code:36876
Deposited On:16 Apr 2011 14:05
Last Modified:17 May 2016 19:48

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