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Alternative N-terminal regions of Drosophila myosin heavy chain II regulate communication of the purine binding loop with the essential light chain

Bloemink, Marieke J., Hsu, Karen H., Geeves, Michael A., Bernstein, Sanford I. (2020) Alternative N-terminal regions of Drosophila myosin heavy chain II regulate communication of the purine binding loop with the essential light chain. Journal of Biological Chemistry, . ISSN 0021-9258. E-ISSN 1083-351X. (doi:10.1074/jbc.RA120.014684) (KAR id:82584)

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https://doi.org/10.1074/jbc.RA120.014684

Abstract

We investigated the biochemical and biophysical properties of one of the four alternative exon-encoded regions within the Drosophila myosin catalytic domain. This region is encoded by alternative exons 3a and 3b and includes part of the N-terminal β–barrel. Chimeric myosin constructs (IFI-3a and EMB-3b) were generated by exchanging the exon 3-encoded areas between native slow embryonic body wall (EMB) and fast indirect flight muscle myosin isoforms (IFI). We found that this exchange alters the kinetic properties of the myosin S1 head. The ADP release rate (k-D) in the absence of actin is completely reversed for each chimera compared to the native isoforms. Steady-state data also suggest a reciprocal shift, with basal and actin-activated ATPase activity of IFI-3a showing reduced values compared to wild-type IFI, whereas for EMB-3b these values are increased compared to wild-type EMB. In the presence of actin, ADP affinity (KAD) is unchanged for IFI-3a, compared to IFI, but ADP-affinity for EMB-3b is increased, compared to EMB, and shifted towards IFI values. ATP-induced dissociation of acto-S1 (K1k+2) is reduced for both exon 3 chimeras. Homology modeling, combined with a recently reported crystal structure for Drosophila EMB, indicate that the exon 3 encoded region in the myosin head is part of the communication pathway between the nucleotide binding pocket (purine-binding loop) and the essential light chain, emphasizing an important role for this variable N-terminal domain in regulating acto-myosin cross-bridge kinetics, in particular with respect to the force-sensing properties of myosin isoforms.

Item Type: Article
DOI/Identification number: 10.1074/jbc.RA120.014684
Uncontrolled keywords: sequence alignment, protein structure-function, force-sensing, fluorescence kinetics, actin, muscle, homology modeling, myosin
Subjects: Q Science
Divisions: Divisions > Division of Natural Sciences > School of Biosciences
Depositing User: Michael Geeves
Date Deposited: 24 Aug 2020 14:03 UTC
Last Modified: 25 Aug 2020 09:12 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/82584 (The current URI for this page, for reference purposes)
Geeves, Michael A.: https://orcid.org/0000-0002-9364-8898
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