The shortening of the N‐terminus of myosin essential light chain A1 influences the interaction of heavy meromyosin with actin

Abstract

The effects resulting from the removal of the N-terminus of heavy meromyosin (HMM) A1 light chain by papain digestion are investigated. The fluorometry of TRITCphalloidin labelled actin in ghost fibers is used as a tool for sensing conformational changes of rigor complex of phosphorylated and dephosphorylated HMM with actin filament. The experiments were performed both under conditions assuring saturation of RLC with magnesium cation (4 mM EGTA) or calcium cation (0.1 mM CaCI2), and in constant presence of 1 mM magnesium chloride. HMM native and with A1 shortened from the N-terminus is used. As it was observed previously rigor complex of actin filament and native HMM shows sensitivity to the kind of cation saturating RLC and to the phosphorylation status of RLC. In particular, the sin20 parameter of actin bound rhodamine-phalloidin fluorescence polarization representing roughly the flexibility of actin filament HMM complex changes significantly with the changes of RLC phosphorylation and cation saturation. Removal of the N-terminus of A1 reduces this sensitivity to cation and phosphorylation both in the case of dephosphorylated and phosphorylated HMM. Our results suggest that the N-terminus of A1 plays significant role in the rigor interaction of myosin heads with actin and is involved in modulatory function of RLC in this interaction.

Proteomics - Human Diseases and Protein Functions

“…It has been described that the amino terminus of MLC1 interacts with the carboxy terminus of actin during contraction (Andreev and Borejdo 1999;Efimova et al 1998;Henry et al 1985;Milligan et al 1990;Miyanishi et al 2002;Morano et al 1995;Nieznanska et al 1998;Nieznanska et al 2002;Nieznanski et al 2003;Timson et al 1999;Trayer et al 1987;VanBuren et al 1994). This interaction of MLC1 with actin suggests an important role of MLC1 in the regulation of contraction.…”

Posttranslational Modifications of Myosin Light Chains Determine the Protein Fate

“…The nomenclature for myosin light chains is not always obvious and for this manuscript we will refer to MLC1 as the full length myosin light chain present in the sarcomeres of the ventricle. It has been described that the amino terminus of MLC1 interacts with the carboxy terminus of actin during contraction (Andreev and Borejdo 1999; Efimova et al 1998;Henry et al 1985;Milligan et al 1990;Miyanishi et al 2002;Morano et al 1995;Nieznanska et al 1998;Nieznanska et al 2002;Nieznanski et al 2003;Timson et al 1999;Trayer et al 1987;VanBuren et al 1994). This interaction of MLC1 with actin suggests an important role of MLC1 in the regulation of contraction.…”