Analysis of myosin heavy chain functionality in the heart

Maike Krenz, Atsushi Sanbe, Florence Bouyer-Dalloz, James Gulick, Raisa Klevitsky, Timothy E. Hewett, Hanna E. Osinska, John N. Lorenz, Christine Brosseau, Andrea Federico, Norman R. Alpert, David M. Warshaw, M. Benjamin Perryman, Steve M. Helmke, Jeffrey Robbins

Research output: Contribution to journalArticlepeer-review

86 Scopus citations


Comparison of mammalian cardiac α- and β-myosin heavy chain isoforms reveals 93% identity. To date, genetic methodologies have effected only minor switches in the mammalian cardiac myosin isoforms. Using cardiac-specific transgenesis, we have now obtained major myosin isoform shifts and/or replacements. Clusters of non-identical amino acids are found in functionally important regions, i.e. the surface loops 1 and 2, suggesting that these structures may regulate isoform-specific characteristics. Loop 1 alters filament sliding velocity, whereas Loop 2 modulates actin-activated ATPase rate in Dictyostelium myosin, but this remains untested in mammalian cardiac myosins. α → β isoform switches were engineered into mouse hearts via transgenesis. To assess the structural basis of isoform diversity, chimeric myosins in which the sequences of either Loop 1 + Loop 2 or Loop 2 of α-myosin were exchanged for those of β-myosin were expressed in vivo. 2-fold differences in filament sliding velocity and ATPase activity were found between the two isoforms. Filament sliding velocity of the Loop 1 + Loop 2 chimera and the ATPase activities of both loop chimeras were not significantly different compared with α-myosin. In mouse cardiac isoforms, myosin functionality does not depend on Loop 1 or Loop 2 sequences and must lie partially in other non-homologous residues.

Original languageEnglish (US)
Pages (from-to)17466-17474
Number of pages9
JournalJournal of Biological Chemistry
Issue number19
StatePublished - May 9 2003

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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