期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1993
卷号：90
期号：14
页码：6791-6795
DOI：10.1073/pnas.90.14.6791
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：A well-known indication that a nucleotide has bound to myosin is the enhancement of the fluorescence of a specific tryptophan in the "subfragment 1" segment of the protein. Empirically the effect has been enormously useful in myosin enzymology. But beyond an early suggestion that it arises from a purine-tryptophan charge-transfer complex, the mechanism of the effect has not been considered. Here we consider the alternative that it arises from an ionizable group (either another residue or the phosphate of the nucleotide) whose proximity to the tryptophan is altered by substrate binding. We study this possibility by studying the interaction of an ionizable residue and tryptophan when both are incorporated in a diketopiperazine structure. The geometry of the situation is inferred from molecular mechanics simulations. Unexpectedly, the best explanation seems to be that the field of the imposed charge, acting across space, affects events in the excited state of the indole.
