Structural aspects of skeletal muscle G-actin molecule as studied by proteolytic digestion: effect of nucleotide.
Trypsin and chymotrypsin were used as probes of conformation of G-actin molecule. The pattern of fragments produced has been analyzed by sodium dodecyl sulfate gel electrophoresis. G-actin is known to be nonrefractory to proteolysis [Jacobson, G.R., and Rosenbusch, J.P. (1976) Proc. Natl. Acad. Sci. U.S.A. 73, 2742-2746]. It is really true that G-actin is cut easily into a 33-kDa fragment by trypsin or chymotrypsin, but only when free ATP is present in the medium. After the removal of free ATP from the medium, G-actin became more refractory to proteolysis. The amounts of degradation of G-actin depended on the ATP concentration in the medium with saturating at about 0.5 mM. epsilon-ADP also had the effect and its fluorescence spectrum was changed on the addition of G-actin. After the removal of free ATP, G-actin still bound 1 mol/mol of ATP. So, the present results suggest the presence of a second ATP interaction site on G-actin and that ATP interaction at this site induces conformational changes in G-actin molecule.
Hozumi
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Department of Physiology, Nagoya City University Medical School, Japan.
D000199:Actins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000818:Animals; D001665:Binding Sites; D001704:Biopolymers; D055598:Chemical Phenomena; D002621:Chemistry; D002918:Chymotrypsin; D006868:Hydrolysis; D009132:Muscles; D011485:Protein Binding; D011487:Protein Conformation; D011817:Rabbits; D013050:Spectrometry, Fluorescence; D014357:Trypsin
D000199:Actins; D001704:Biopolymers; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D002918:Chymotrypsin; D014357:Trypsin