Thin Filament Regulation and Ionic Interactions between the N-terminal Region in Actin and Troponin

Abstract

The N-terminal region in actin has been shown to interact with both myosin and troponin (Tn) during the cross-bridge cycle and in regulation. To study the role of this region in regulation, we used yeast actin mutants with increased and decreased numbers of acidic residues. The mutants included D24A/D25A, with Asp(24) and Asp(25) replaced with alanines; DNEQ, with the substitution of Asp(2) and Glu(4) with their amide analogs; and 4Ac, with Glu(3) and Asp(4) inserted in lieu of Ser(3). In the in vitro motility assay, using reconstituted regulated thin filaments, the sliding speeds of DNEQ, D24A/D25A, and 4Ac were similar at all pCa values. Thus, Ca(2+)-sensitivity of the thin filaments and the inhibitory function of TnI appear to be insensitive to changes in charge (+/-2) at the N-terminus of actin, suggesting little, if any, role of that actin region in regulation. A Ca(2+)-independent conformational change in that region was detected upon troponin binding to actin-Tm via an increase in the fluorescence of a pyrene probe attached to another yeast actin mutant that we used (Cys(1)).

A Computational Exploration of the Interactions of the Green Tea Polyphenol (–)-Epigallocatechin 3-Gallate with Cardiac Muscle Troponin C

“…Therefore the biochemical effects of these polyphenols are of great interest as they could potentially lead to prevention or new treatments of heart disease. [8], [13], [14].…”

Plant Vegetative and Animal Cytoplasmic Actins Share Functional Competence for Spatial Development with Protists

“…Several observations support this model. First, phylogenetic clustering of the actin sequences examined demonstrated that the animal cytoplasmic actins and two of the protist actin sequences (i.e., Mb-ACT and Ac-ACT1), which suppressed loss of plant actin function, are quite distinct in their sequences from the plant actins ( Figure 1B role has been shown for the N-terminal region containing several acidic amino acids (Lasa et al, 1997;Hinz et al, 2002;Wong et al, 2002;Lu et al, 2005). Therefore, we were surprised to observe that the animal cytoplasmic actins (i.e., Hs-ACTG1, Hs-ACTB, and Ci-ACTB1) and the protist actins (i.e., Ac-ACT1 and Mb-ACT), which are two amino acids shorter than all plant actins at the N terminus (see Supplemental Figure 2 online), efficiently substituted for plant actins.…”

Yeast actin with a subdomain 4 mutation (A204C) exhibits increased pointed-end critical concentration

“…In yeast actin, only 1 cysteine (Cys-374) is readily modified by chemical means. Therefore, substituting Cys-374 with another amino acid results in a Cys-light version of actin that can be used to introduce cysteine residues at other locations throughout the actin structure, as performed in various previous studies (Feng et al 1997;Kim et al 2000;Orlova et al 2004;Shvetsov et al 2002;Wong et al 2002). These studies showed that the substitution of Cys-374 had no significant effect on the properties of actin.…”