The eye lens protein αA-crystallin of the blind mole rat Spalax ehrenbergi

Abstract

The rudimentary eyes of the mole rat Spalax ehrenbergi have lost their visual function, but are still required for the control of circadian rhythms. It has previously been found that αA-crystallin, a major eye lens protein in other mammals, evolved much faster in the mole rat than in rodents with normal vision. Yet, although mole rat αA-crystallin seems superfluous as a lens protein, its rate of change is still much slower than that of pseudogenes, suggesting some remaining function. The authors therefore studied the structure and function of recombinant mole rat αA-crystallin. Circular dichroism (CD), tryptophan fluorescence and gel permeation analyses indicated that the overall structure and stability of mole rat αA-crystallin are comparable to that of rat αA-crystallin. However, the chaperone-like activity of mole rat αA-crystallin is considerably lower than that of its rat orthologue. Two-dimensional NMR spectroscopy of mole rat αA-crystallin suggests that this may be in part due to a diminished flexibility of the C-terminal extension, which is thought to be important for the chaperoning capacity. Overall, mole rat αA-crystallin appears to still be a viable protein, confirming that it has some as yet elusive role, despite the loss of its primary lens function. Show more