N-Terminus of Cardiac Myosin Essential Light Chain Modulates Myosin Step-Size
In: Biochemistry, Jg. 55 (2015-12-29), S. 186-198
Online
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Zugriff:
Muscle myosin cyclically hydrolyzes ATP to translate actin. Ventricular cardiac myosin (βmys) moves actin with three distinct unitary step-sizes resulting from its lever-arm rotation and with step-frequencies that are modulated in a myosin regulation mechanism. The lever-arm associated essential light chain (vELC) binds actin by its 43 residue N-terminal extension. Unitary steps were proposed to involve the vELC N-terminal extension with the 8 nm step engaging the vELC/actin bond facilitating an extra ~19 degrees of lever-arm rotation while the predominant 5 nm step forgoes vELC/actin binding. A minor 3 nm step is the unlikely conversion of the completed 5 to the 8 nm step. This hypothesis was tested using a 17 residue N-terminal truncated vELC in porcine βmys (Δ17βmys) and a 43 residue N-terminal truncated human vELC expressed in transgenic mouse heart (Δ43αmys). Step-size and step-frequency were measured using the Qdot motility assay. Both Δ17βmys and Δ43αmys had significantly increased 5 nm step-frequency and coincident loss in the 8 nm step-frequency compared to native proteins suggesting the vELC/actin interaction drives step-size preference. Step-size and step-frequency probability densities depend on the relative fraction of truncated vELC and relate linearly to pure myosin species concentrations in a mixture containing native vELC homodimer, two truncated vELCs in the modified homodimer, and one native and one truncated vELC in the heterodimer. Step-size and step-frequency, measured for native homodimer and at two or more known relative fractions of truncated vELC, are surmised for each pure species by using a new analytical method.
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N-Terminus of Cardiac Myosin Essential Light Chain Modulates Myosin Step-Size
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Autor/in / Beteiligte Person: | Wang, Yihua ; Kazmierczak, Katarzyna ; Szczesna-Cordary, Danuta ; Ajtai, Katalin ; Burghardt, Thomas P. |
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Zeitschrift: | Biochemistry, Jg. 55 (2015-12-29), S. 186-198 |
Veröffentlichung: | American Chemical Society (ACS), 2015 |
Medientyp: | unknown |
ISSN: | 1520-4995 (print) ; 0006-2960 (print) |
DOI: | 10.1021/acs.biochem.5b00817 |
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