This content is PDF only. Please click on the PDF icon to access.
Abstract
Calcium is capable of discriminating between low and high molecular weight species of bovine alpha crystallin. If native alpha crystallin of molecular weight 15 x 106 or greater is deaggregated in 7M urea and then reaggregated by removal of the dissociating agent only low molecular weight aggregates are obtained. However, in the presence of calcium, reaggregation of the subunits to species of 50 x 106 or greater is observed. With native low molecular weight alpha crystallin, calcium has no effect upon the reaggregation process. Reaggregation of the isolated polypeptide chains of low molecular weight alpha crystallin is also not affected by calcium. Only an atypical A polypeptide fraction from high molecular weight alpha crystallin has been shown to reaggregate to high molecular weight aggregates in the presence of calcium. A magnesium concentration three times greater than that of calcium is required to produce a similar effect upon the reaggregation process. Equimolar concentrations of ethylenediaminetetraacetate (EDTA), glutathione, oxidized glutathione, or alanine were shown to completely inhibit the calcium effect.