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R S Adelstein

Publications and source records attributed to R S Adelstein.

120 records · Page 7Linked to original sources
PubMed1973

Phosphorylation of human platelet myosin.

A preparation extracted from human blood platelets, which incorporates (32)P from gamma-labeled AT(32)P into one of the two light chains of platelet myosin and platelet myosin head is described. This phosphorylation, which appears to be due to an endogenous kinase, is specific for the myosin light chain in that no other protein extracted in 0.6 M KCl-15 mM Tris.HCl (pH 7.5) is phosphorylated. The phosphorylated light chain, which has been purified by gel filtration, releases the covalently bound phosphate after incubation in alkali and not after incubation in acid.

Adenosine Triphosphate↗
PubMed1973

Complete amino-acid sequence of actin of rabbit skeletal muscle.

The complete amino-acid sequence of actin of rabbit skeletal muscle was determined. The actin polypeptide chain is composed of 374 residues, including one residue of the unusual amino acid N(r)-methyl histidine, and has a calculated molecular weight of 41,785. The sequence of actin was determined by isolating the peptides produced by cleavage of the protein with cyanogen bromide, determining the sequence of these peptides, and establishing their order within the molecule. This study represents the first complete determination of the aminoacid sequence of a myofibrillar protein. Comparison of this sequence with peptides from actins isolated from different sources indicates that the sequence of actin is highly conserved.

Actins↗
PubMed1972

Isolation and characterization of myosin from cloned mouse fibroblasts.

Myosin has been isolated from cloned mouse fibroblasts, line L-929. Fibroblast myosin: (i) binds to rabbit muscle actin and is dissociated from it by ATP, (ii) has an ATPase activity that is suppressed by Mg(2+) in 0.6 M KCl and is activated by rabbit muscle actin in the presence of Mg(2+) in 14 mM KCl, (iii) forms thin bipolar aggregates in 0.1 M KCl when viewed in the electron microscope, (iv) possesses a heavy chain with the same mobility as muscle myosin (molecular weight 200,000) in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In these respects, fibroblast myosin appears to be similar to muscle myosin in structure and function.

Actins↗
PubMed1971

Isolation and characterization of myosin and two myosin fragments from human blood platelets.

Platelet myosin (thrombosthenin M) and two additional proteins corresponding to the head and rod portion of the myosin molecule have been prepared from human blood platelets. Characterization of these proteins by SDS-polyacrylamide gel electrophoresis, actin binding studies, assay of enzymic ATPase activity, and electron microscopy has shown that the platelet contractile proteins closely resemble the corresponding muscle proteins. Platelet myosin and platelet myosin-head bind to both muscle and platelet actin and have an EDTA + K-stimulated ATPase activity, which is suppressed by Mg(2+) in high salt concentration, whereas platelet rod does not possess either of these properties; platelet myosin and platelet myosin rod aggregate to form thick filaments at low ionic strength. Both intact platelet myosin and myosin head form typical arrowhead-shaped complexes with either platelet or muscle F-actin.

Actins↗
PubMedDate not supplied

Phorbol ester-induced activation of human platelets is associated with protein kinase C phosphorylation of myosin light chains.

Phosphorylation of the 20,000 molecular weight (MW) light chain of platelet myosin is associated with the activation of platelets and subsequent release of platelet granules, and the protein kinase catalysing this phosphorylation has been identified as the Ca2+/calmodulin-dependent enzyme, myosin light chain kinase. Tumour-promoting phorbol esters such as 12-O-tetradecanoylphorbol-13-acetate (TPA), which activate Ca2+-activated, phospholipid-dependent protein kinase (protein kinase C), can also cause platelet aggregation and phosphorylation of a 20,000-MW peptide in blood platelets. It was therefore of interest to ascertain whether the 20,000-MW peptide phosphorylated in platelets was the light chain of myosin and whether TPA-induced phosphorylation of the 20,000-MW peptide could be differentiated from thrombin-induced phosphorylation. We now report that TPA-induced activation of platelets is associated with the phosphorylation of the 20,000-MW light chain of myosin, that it appears to be mediated mainly through protein kinase C and that the site phosphorylated in the myosin light chain is distinct from that phosphorylated by myosin light chain kinase.

Blood Platelets↗
PubMedDate not supplied

Characterization of myosin from patients with asymmetric septal hypertrophy.

Human cardiac myosin isolated from operatively obtained samples of ventricular septum and left ventricular free wall of patients with asymmetric septal hypertrophy (ASH) was compared, with respect to structural and enzymatic properties, to myosin isolated from hearts of patients without heart disease. The following parameters were studied: 1) activation of myosin ATPase activity by K+-EDTA and Ca2+,2) molecular weight of the heavy and light chains of myosin as determined by electrophoretic migration in SDS-polyacrylamide gels, and 3) ability to form bipolar aggregates at low ionic strength, as examined by electron microscopy. No difference was present in any of these parameters between human cardiac myosin from patients with ASH and from patients without heart disease. Thus, the genetic defect present in patients with ASH is not expressed in the particular structural and functional characteristics of myosin evaluated in this study.

Actomyosin↗