Alternative relay domains of Drosophila melanogaster myosin differentially affect ATPase activity, in vitro motility, myofibril structure and muscle function

JOURNAL OF MOLECULAR BIOLOGY

卷:379

Article

Swank, Douglas M.^2,3  Bernstein, Sanford I.¹ 

[1] San Diego State Univ, Inst Mol Biol, Dept Biol, San Diego, CA 92182 USA

[2] Rensselaer Polytech Inst, Ctr Biotechnol & Interdisciplinary Studies, Troy, NY 12180 USA

[3] Rensselaer Polytech Inst, Dept Biol, Troy, NY 12180 USA

关键词: myosin;    Drosophila;    relay domain;    protein isoforms;    muscle;   

DOI  :  10.1016/j.jmb.2008.04.010

来源: Elsevier

【 摘 要 】

The relay domain of myosin is hypothesized to function as a communication pathway between the nucleotide-binding site, actin-binding site and the converter domain. In Drosophila melanogaster, a single myosin heavy chain gene encodes three alternative relay domains. Exon 9a encodes the indirect flight muscle isoform (IFI) relay domain, whereas exon 9b encodes one of the embryonic body wall isoform (EMB) relay domains. To gain a better understanding of the function of the relay domain and the differences imparted by the IFI and the EMB versions, we constructed two transgenic Drosophila lines expressing chimeric myosin heavy chains in indirect flight muscles lacking endogenous myosin. One expresses the IFI relay domain in the EMB backbone (EMB-9a), while the second expresses the EMB relay domain in the IFI backbone (IFI-9b). Our studies reveal that the EMB relay domain is functionally equivalent to the IFI relay domain when it is substituted into IFI. Essentially no differences in ATPase activity, actin-sliding velocity, flight ability at room temperature or muscle structure are observed in IFI-9b compared to native IFI. However, when the EMB relay domain is replaced with the IFI relay domain, we find a 50% reduction in actin-activated ATPase activity, a significant increase in actin affinity, abolition of actin sliding, defects in myofibril assembly and rapid degeneration of muscle structure compared to EMB. We hypothesize that altered relay domain conformational changes in EMB-9a impair intramolecular communication with the EMB-specific converter domain. This decreases transition rates involving strongly bound actomyosin states, leading to a reduced ATPase rate and loss of actin motility. (c) 2008 Elsevier Ltd. All rights reserved.

【 授权许可】

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