The quaternary structure of XXXX -germ @entity492 transcarbamoylase.

@entity526 @entity13253 @entity969 @entity21100 @entity492 @entity2975 @entity3505 @entity214
1. The molecular mass of @entity492 transcarbamoylase purified from @entity3505 germ was found to be 101kDa by @entity969 -density-gradient centrifugation, 103kDa by gel-filtration chromatography and 108kDa by @entity2975 -gel electrophoresis. A mean value of 104 +/- 11kDa was obtained by pooling several replicate results from each method. 2. @entity2975 -gel electrophoresis in the presence of @entity214 indicated a single size of polypeptide chain of mean molecular mass 37 +/- 4kDa. The ratio of the mean molecular masses of the active and denatured enzymes is 2.8.3. When the active enzyme was covalently cross-linked at a low protein concentration by @entity13253 , and then examined electrophoretically under denaturing conditions, three size species were observed to predominate, of apparent molecular masses 36, 77 and 106kDa respectively. 4. These results indicate that the intact, fully regulatory enzyme is a simple trimer, slightly larger than the trimeric "catalytic subunit' of the @entity492 transcarbamoylase from @entity526 [Weber (1968) Nature (London) 218, 1116-1118]. The prevalence of trimeric structures amongst @entity21100 -transferase enzymes is discussed.
