Abstract
Abstract: :
Purpose: There are many missense crystallin genes that have been identified in autosomal dominant congenital cataracts. The CRYBB2 (Q155* truncation) was reported to be associated with cerulean cataract. ßB2–crystallin is the major ß–crystallin component and is a dimer under physiological conditions. The interaction domains were speculated to be the ß–strands. It is not known how the Q155* and ß–strand deleted mutations affect protein–protein interactions and other biophysical properties. Methods: Site–specific mutations were performed to obtain the Q155* and other ß–strand deleted or deficient mutants (V46E, V54E, F132E, and V144E). Protein–protein interactions were screened by a mammalian two–hybrid system assay. Some biophysical properties were studied with spectroscopy and chromatography. Results:Decreases of protein–protein interactions were observed for all ß–strand deleted mutants except V46E with the greatest decrease for the V144E. The Q155* mutation retains dimer status but changes conformation and loses stability. Conclusions: The sequence around V144 that formed a ß–strand appears to play a major role in dimerization. The Q155* mutation causes adverse changes in protein biophysical properties that contribute to cataract formation.
Keywords: cataract • crystallins • mutations