Prevention of the inactivation of glutathione reductase by fructation using human alpha-crystallin.

Specific functions have not been assigned to lens crystallins. It was assumed that they had been recruited to the lens to refract light. Mammali an aaystallin, which may represent up to 50% of the total crystallin [I], is sequentially related to heat shock proteins [2], with sauctural and functional similarities to the mouse small heat shock protein Hsp25 [3]. aB-Crystallin has been found outside the lens, where its appearance or increase was often associated with various stress-related conditions, including neurodegenerative diseases [4,5]. Heat shock and stress proteins have been shown to act as molecular chaperones, preventing i n c o m folding of other proteins during synthesis or when exposed to potentially denaturing conditions [6]. Honvitz [7] demonstrated that bovine a-crystallin was capable of acting like a chaperone in that it prevented the heatinduced aggregation of various proteins, including other crystallins. We showed that this protein pvented the fructation-induced inactivation of glutathione reductase [8]. It was investigated whether human acrystallin was also able to protect this enzyne. Human a-crystallin was isolated by the method of Slingsby and Bateman [9] using a Sephacryl S-3OOHR size-exclusion gel chromatography column [8] . We used the same glutathione reductase inactivation system as befare [8 ] , incubating human a-crystallin at a weight ratio of 1:l to the enzyme, and various