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Nat Cell Biol. 2001 Nov;3(11):1025-9.

Loss of SM-B myosin affects muscle shortening velocity and maximal force development.

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  • 1Department of Physiology and Cell Biology, College of Medicine and Public Health, The Ohio State University, 304 Hamilton Hall, 1645 Neil Avenue, Columbus, Ohio 43210, USA.

Abstract

We used an exon-specific gene-targeting strategy to generate a mouse model deficient only in the SM-B myosin isoform. Here we show that deletion of exon-5B (specific for SM-B) in the gene for the heavy chain of smooth muscle myosin results in a complete loss of SM-B myosin and switching of splicing to the SM-A isoform, without affecting SM1 and SM2 myosin content. Loss of SM-B myosin does not affect survival or cause any overt smooth muscle pathology. Physiological analysis reveals that absence of SM-B myosin results in a significant decrease in maximal force generation and velocity of shortening in smooth muscle tissues. This is the first in vivo study to demonstrate a functional role for the SM-B myosin isoform. We conclude that the extra seven-residue insert in the surface loop 1 of SM-B myosin is a critical determinant of crossbridge cycling and velocity of shortening.

PMID:
11715025
[PubMed - indexed for MEDLINE]
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