title: The functional domains of human ventricular myosin light chain 1.
abstract: The biological functions of the myosin light chain 1 (LC1) have not been clearly elucidated yet. In this work we cloned and expressed N- and C- terminal fragments of human ventricular LC1 (HVLC1) containing amino acid residues 1-98 and 99-195 and two parts, NN and NC of N fragment in GST-fusion forms, respectively. Using GST pull-down assay, the direct binding experiments of LC1 with rat cardiac G-actin, F-actin and thin filaments, as well as rat cardiac myosin heavy chain (RCMHC) have been performed. Furthermore, the recombinant complexes of rat myosin S1 with N- and C-fragments, as well as the whole molecular of HVLC1 were generated. The results suggested that both binding sites of HVLC1 for actin and myosin heavy chain are positioned in its N-terminal fragment, which may contain several actin-binding sites in tandem. The polymerization of G-actin, the tropomyosin and troponin molecules located in the thin filaments do not hinder the binding of N-terminal fragment of HVLC1 with actin and thin filaments in vitro. The recombinant complex of rat cardiac myosin S1 (RCMS1) with N fragment of HVLC1 greatly decreased actin-activated Mg(2+)-ATPase activity for lack of C fragment. We conclude that the N-fragment is the binding domain of human ventricular LC1, whereas the C-fragment serves as a functional domain, which may be more involved in the modulation of the actin-activated ATPase activity of myosin.
mesh_terms: D000199:Actins / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D006352:Heart Ventricles / Q000737:chemistry*; D006801:Humans; D008274:Magnesium / Q000378:metabolism; D009206:Myocardium / Q000737:chemistry; D018994:Myosin Light Chains / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015879:Myosin Subfragments; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats
chemical_list: D000199:Actins; D018994:Myosin Light Chains; D015879:Myosin Subfragments; D010446:Peptide Fragments; D000251:Adenosine Triphosphatases; D008274:Magnesium; D011188:Potassium; D002118:Calcium