Binding of ADP and adenosine 5′‐[β,γ‐imido]triphosphate to insect flight muscle fibrils

Josep A. BIOSCA, Evan EISENBERG, Mary C. REEDY, Michael K. REEDY

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Abstract

We have studied the binding of ADP and adenosine 5′‐[β,γ‐imido]triphosphate (AdoPP[NH]P) to insect flight muscle fibrils. We find that 25% of the myosin heads, presumably those which do not interact with actin, bind AdoPP[NH]P with a binding constant greater than 3 × 106 M−1, similar to the binding constant of the same compound to the rabbit myosin heads which do not overlap with actin. The remaining heads in insect myofibrils bind AdoPP[NH]P with an association constant of 8 × 103 M−1, which is eight times stronger than the affinity of this compound for rabbit myosin heads in overlap with actin. Therefore, in contrast to the situation with rabbit myofibrils where AdoPP[NH]P binds much more weakly than ADP, with insect myofibrils these two adenosine phosphates bind with almost equal affinity. This is consistent with the numerous structural studies on insect flight muscle which were interpreted on the basis that most of the actomyosin sites were saturated with nucleotide at an AdoPP[NH]P concentration of 1 mM. Copyright © 1990, Wiley Blackwell. All rights reserved
Original languageEnglish
Pages (from-to)395-399
JournalEuropean Journal of Biochemistry
Volume189
Issue number2
DOIs
Publication statusPublished - 1 Jan 1990

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