Variable N-terminal Regions of Muscle Myosin Heavy Chain Modulate ATPase Rate and Actin Sliding Velocity

We integratively assessed the function of alternative versions of a region near the N terminus ofDrosophila muscle myosin heavy chain (encoded by exon 3a or 3b). We exchanged the alternative exon 3 regions between an embryonic isoform and the indirect flight muscle isoform. Each chimeric myosin was...

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Bibliographic Details
Published in:The Journal of biological chemistry 2003-05, Vol.278 (19), p.17475-17482
Main Authors: Swank, Douglas M., Knowles, Aileen F., Kronert, William A., Suggs, Jennifer A., Morrill, George E., Nikkhoy, Massoud, Manipon, Gracielle G., Bernstein, Sanford I.
Format: Article
Language:English
Subjects:
Actins - metabolism
Adenosine Triphosphatases - metabolism
Amino Acid Sequence
Animals
Drosophila
Molecular Motor Proteins - genetics
Molecular Sequence Data
Muscle, Skeletal - metabolism
Myosin Heavy Chains - genetics
Myosin Heavy Chains - metabolism
Protein Conformation
Sequence Analysis
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Summary:We integratively assessed the function of alternative versions of a region near the N terminus ofDrosophila muscle myosin heavy chain (encoded by exon 3a or 3b). We exchanged the alternative exon 3 regions between an embryonic isoform and the indirect flight muscle isoform. Each chimeric myosin was expressed in Drosophila indirect flight muscle, in the absence of other myosin isoforms, allowing for purified protein analysis and whole organism locomotory studies. The flight muscle isoform generates higher in vitro actin sliding velocity and solution ATPase rates than the embryonic isoform. Exchanging the embryonic exon 3 region into the flight muscle isoform decreased ATPase rates to embryonic levels but did not affect actin sliding velocity or flight muscle ultrastructure. Interestingly, this swap only slightly impaired flight ability. Exchanging the flight muscle-specific exon 3 region into the embryonic isoform increased actin sliding velocity 3-fold and improved indirect flight muscle ultrastructure integrity but failed to rescue the flightless phenotype of flies expressing embryonic myosin. These results suggest that the two structural versions of the exon 3 domain independently influence the kinetics of at least two steps of the actomyosin cross-bridge cycle.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M212727200