Spin labbelling of D-glyceraldehyde-3-phosphate dehydrogenase with specific reagents

Elek, G and Sajgó, M and Grigorian, GL and Chibrikin, VM and Keleti, Tamás (1972) Spin labbelling of D-glyceraldehyde-3-phosphate dehydrogenase with specific reagents. ACTA BIOCHIMICA ET BIOPHYSICA HUNGARICA, 7 (2). pp. 119-131. ISSN 0237-6261

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Abstract

Blocking of D-glyceraldehyde-3-phosphate dehydrogenase with spin-labelled iodoacetate or iodoacetamide results in a spectrum which can be regarded as a sum of ESR signals of rotationally slightly hindered and immobilized radicals. In the apoenzyme whose reactive SH-group is blocked with spin-labelled iodoacetate the proportion of immobilized radicals increases on the addition of NAD. The inhibitory effect of non-labelled iodoacetate differs from that of the spin-labelled reagent. In contrast to the non-labelled alkylating agents, the spin-labelled compounds induce structural changes in the enzyme and consequently SH-groups other that the reactive ones are also blocked. In case of spin-labelled alkylating reagents the sulfhydryls that reacted after the reactive ones belong to Cys-153. It seems reasonable to assume that there is a cleft on the surface of the protein near the reactive SH, the width of which is comparable to the maximal diameter of spin-labelled reagent, and that the peptide sequence between residues Cys-149 and Cys-153 is of non-helical structure.

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