Abstract
Glycogenin, the autoglucosyltransferase that initiates thede novobiosynthesis of glycogen, photoaffinity labeled with [β32P]5-azido-UDP-glucose. The photoinsertion of the azidouridine derivative showed activating ultraviolet light dependency, saturation effects, and inhibition by UDP-glucose, thus demonstrating the specificity of the interaction. In the absence of Mn2+, the requirement for the catalytic activity of glycogenin, the photolabeling decreased by 70%. Competitive binding experiments indicated that the pyrophosphate or a phosphate was the moiety of UDP-glucose implicated in the strongest interaction at the binding site. Proteolytic digestion of photolabeled glycogenin resulted in the identification of two labeled fragments, 89–143 and 168–233, that carried the uridine binding sites. This is the first report of the region of glycogenin that harbors the UDP-glucose-binding domain.
Published Version
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