Analysis of Myosin Heavy Chain Functionality in the Heart

Autor: Jeffrey Robbins, Christine Brosseau, Norman R. Alpert, Hanna Osinska, John N. Lorenz, Andrea Federico, David M. Warshaw, Raisa Klevitsky, M. Benjamin Perryman, Maike Krenz, Florence Bouyer-Dalloz, Steve M. Helmke, James Gulick, Timothy E. Hewett, Atsushi Sanbe
Rok vydání: 2003
Předmět:
Zdroj: Journal of Biological Chemistry. 278:17466-17474
ISSN: 0021-9258
Popis: Comparison of mammalian cardiac alpha- and beta-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. Alpha --beta 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 alpha-myosin were exchanged for those of beta-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 alpha-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.
Databáze: OpenAIRE