Alternative relay and converter domains tune native muscle myosin isoform function in Drosophila.
J Mol Biol
; 416(4): 543-57, 2012 Mar 02.
Article
em En
| MEDLINE
| ID: mdl-22226837
ABSTRACT
Myosin isoforms help define muscle-specific contractile and structural properties. Alternative splicing of myosin heavy chain gene transcripts in Drosophila melanogaster yields muscle-specific isoforms and highlights alternative domains that fine-tune myosin function. To gain insight into how native myosin is tuned, we expressed three embryonic myosin isoforms in indirect flight muscles lacking endogenous myosin. These isoforms differ in their relay and/or converter domains. We analyzed isoform-specific ATPase activities, in vitro actin motility and myofibril structure/stability. We find that dorsal acute body wall muscle myosin (EMB-9c11d) shows a significant increase in MgATPase V(max) and actin sliding velocity, as well as abnormal myofibril assembly compared to cardioblast myosin (EMB-11d). These properties differ as a result of alternative exon-9-encoded relay domains that are hypothesized to communicate signals among the ATP-binding pocket, actin-binding site and the converter domain. Further, EMB-11d shows significantly reduced levels of basal Ca- and MgATPase as well as MgATPase V(max) compared to embryonic body wall muscle isoform (EMB) (expressed in a multitude of body wall muscles). EMB-11d also induces increased actin sliding velocity and stabilizes myofibril structure compared to EMB. These differences arise from exon-11-encoded alternative converter domains that are proposed to reposition the lever arm during the power and recovery strokes. We conclude that relay and converter domains of native myosin isoforms fine-tune ATPase activity, actin motility and muscle ultrastructure. This verifies and extends previous studies with chimeric molecules and indicates that interactions of the relay and converter during the contractile cycle are key to myosin-isoform-specific kinetic and mechanical functions.
Texto completo:
1
Coleções:
01-internacional
Temas:
Geral
Base de dados:
MEDLINE
Assunto principal:
Processamento Alternativo
/
Cadeias Pesadas de Miosina
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Proteínas de Drosophila
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Drosophila melanogaster
Limite:
Animals
Idioma:
En
Revista:
J Mol Biol
Ano de publicação:
2012
Tipo de documento:
Article
País de afiliação:
Estados Unidos