Fluorescence measurements detect changes in scallop myosin regulatory domain

András Málnási-Csizmadia, György Hegyi, Ferenc Tölgyesi, Andrew G. Szent-Györgyi, László Nyitray

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16 Citations (Scopus)

Abstract

Ca2+-induced conformational changes of scallop myosin regulatory domain (RD) were studied using intrinsic fluorescence. Both tile intensity and anisotropy of tryptophan fluorescence decreased significantly upon removal of Ca2+. By making a mutant RD we found that the Ca2+-induced fluorescence change is due mainly to Trp21 of the essential light chain which is located at the unusual Ca2+-binding EF-hand motif of the first domain. This result suggests that Trp21 is in a less hydrophobic and more flexible environment in the Ca2+-free state, supporting a model for regulation based on the 2 Å resolution structure of scallop RD with bound Ca2+ [Houdusse A. and Cohen C. (1996) Structure 4, 21-32]. Binding of the fluorescent probe, 8- anilinonaphthalene-1-sulphonate (ANS) to the RD senses the dissociation of the regulatory light chain (RLC) in the presence of EDTA, by energy transfer from a tryptophan cluster (Trp818, 824, 826, 827) on the heavy chain (HC). We identified a hydrophobic pentapeptide (Leu836-Ala840) at the head-rod junction which is required for the effective energy transfer and conceivably is part of the ANS-binding site. Extension of the HC component of RD towards the rod region results in a larger ANS response, presumably indicating changes in HC-RLC interactions, which might be crucial for the regulatory function of scallop myosin.

Original languageEnglish
Pages (from-to)452-458
Number of pages7
JournalEuropean Journal of Biochemistry
Volume261
Issue number2
DOIs
Publication statusPublished - Apr 15 1999

Keywords

  • Ca binding
  • Fluorescence
  • Myosin light chains
  • Tryptophan

ASJC Scopus subject areas

  • Biochemistry

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