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Biomedical subjects

H A Cole

Publications and source records attributed to H A Cole.

At least 19 recordsLinked to original sources
PubMed1985

Two-site phosphorylation of the phosphorylatable light chain (20-kDa light chain) of chicken gizzard myosin.

When prepared under specified conditions chicken gizzard myosin was obtained which when incubated with ATP gave rise to a diphosphorylated as well as the monophosphorylated form of P light chain. Formation of the diphosphorylated light chain occurred more readily with these myosin preparations, but could also be obtained by prolonged incubation of the isolated whole light chain fraction with kinase preparations from rabbit skeletal and chicken gizzard muscles. Using isolated light chains as substrate the more readily formed monophosphorylated light chain contained serine phosphate while the diphosphorylated form contained serine and threonine phosphates.

Adenosine Triphosphate↗
PubMed1984

Role of myosin light chain kinase in muscle contraction.

In resting striated muscles of the rabbit muscle in vivo, the phosphorylatable light chain is partially phosphorylated. Tetanic stimulation increased the level of phosphorylation more rapidly in fast twitch than in slow twitch muscle. In both types of muscle the rate of dephosphorylation was relatively slow. In rabbit fast twitch muscles, phosphorylation levels persisted significantly above the resting value for some time after posttetanic potentiation had disappeared. The role of myosin light chain kinase in modulating contractile response in striated muscle is uncertain. In vertebrate smooth muscle the role of myosin phosphorylation appears to be different from that in striated muscle despite the general similarity of the actomyosin system in both tissues. Although phosphorylation in vitro increases the Mg2+ -ATPase of actomyosin, a number of features imply that a somewhat complex relationship exists between the level of phosphorylation and the actin activation of the Mg2+ -ATPase in vertebrate smooth muscle. Contrary to many earlier reports, preparations of smooth muscle actomyosin can be obtained with Mg2+ -ATPase activities comparable to those of actomyosin from skeletal muscle. Preliminary evidence is presented that suggests that phosphorylation changes the Ca2+ sensitivity of the Mg2+ -ATPase of smooth muscle actomyosin.

Actomyosin↗
PubMed1983

Phosphorylation of chicken gizzard myosin and the Ca2+-sensitivity of the actin-activated Mg2+-ATPase.

A method is described for the preparation of partially and fully phosphorylated chicken gizzard myosin. When fully phosphorylated it possessed an actin-activated Mg2+-ATPase of similar specific activity to that of mammalian skeletal muscle myosin. The Mg2+-ATPase activity of these preparations was related in a non-linear fashion to increasing phosphorylation of the P light chain. When P light chain phosphorylation occurred during enzymic assay the Mg2+-ATPase activity remained constant. Fully phosphorylated preparations of gizzard myosin possessed an actin-activated Mg2+-ATPase that was not Ca2+-sensitive, whereas the Mg2+-ATPase of partially phosphorylated myosin preparations was Ca2+-sensitive.

Actins↗
PubMed1982

Non-correlation of phosphorylation of the P-light chain and the actin activation of the ATPase of chicken gizzard myosin.

1. The enzymic properties of myosin isolated from chicken gizzard by three different methods have been compared. 2. Although the specific Ca2+-stimulated ATPases of all preparations were similar and high, there were significant differences in the specific activities of the Mg2+-stimulated actomyosin ATPases. 3. There was no direct correlation between the Mg2+-stimulated actomyosin ATPase activity and the extent of P-light-chain phosphorylation in any of the three myosin preparations. 4. A fraction that activates the Mg2+-stimulated actomyosin ATPase of gizzard muscle has been isolated from a gizzard muscle filament preparation. 5. The activator was specific for the Mg2+-activated actomyosin ATPase of smooth muscle. 6. The activator required the addition of calmodulin for full effect.

Actomyosin↗
PubMed1979

Pollution of the sea and its effects.

Marine pollution has been studied under the following groupings of effects; harm to living resources, hazards to human health, reduction of amenities and interference with other users of the sea. This paper is concerned mainly with the first two categories and their interrelation. Apart from certain seabirds affected by oil, the major stocks of marine animals show no evidence of reduction by pollution. Pollution effects are generally insignificant in relation to other factors governing reproductive success, survival, growth and population size. Even in the North Sea, which has received a greatly increased pollution load during the last three decades, both total production of fish and catch per unit of effort (a measure of abundance) of cod, haddock and plaice increased during the 20 years 1950--69. Very recent decreases have been due to over-exploitation but, except in certain estuaries and immediate coastal waters, direct damage by pollution to marine populations and ecosystems is not evident. Pollution effects can, however, be detected by chemical analysis. The paper examines human health risks arising in the marine environment, particularly from contaminated seafood, especially in relation to sewage pollution, metals such as mercury, cadmium and lead, synthetic organic substances and oil.

Animals↗
PubMed1977

The phosphorylation sites of troponin T from white skeletal muscle and the effects of interaction with troponin C on their phosphorylation by phosphorylase kinase.

1. The phosphorylation of troponin T from rabbit white sketetal muscle is catalysed by phosphorylase kinase, but not at a significant rate by bovine 3':5'-cyclic AMP-dependent protein kinase. 2. The amino acid sequences adjacent to the three major phosphorylation sites of troponin T were determined. 3. The serine in the N-terminal peptide (Asx,SerP, Glx)Glu-Val-Glu, is that phosphorylated (SerP, phosphoserine) when the troponin complex is isolated. 4. The other two sites of phosphorylation are located in the sequence Ala-Leu-(Ser, SerP)-Met-Gly-Ala-Asn-Tyr(Ser,SerP)Tyr. 5. When troponin T is phosphorylated in the presence of troponin C, the extent of phosphorylation at each site is considerably decreased. 6. CNBr fragments of troponin T are also phosphorylated by phosphorylase kinase, but the rate of phosphorylation at each site in the CNBr fragments is considerably slower than in the native protein. 7. From these studies it is suggested that troponin C interacts with troponin T in the region containing the two closely situated phosphorylation sites.

Amino Acid Sequence↗
PubMed1975

The phosphorylation of troponin I from cardiac muscle.

1. Troponin I isolated from fresh cardiac muscle by affinity chromatography contains about 1.9 mol of covalently bound phosphate/mol. Similar preparations of white-skeletal-muscle troponin I contain about 0.5 mol of phosphate/mol. 2. A 3':5'-cyclic AMP-dependent protein kinase and a protein phosphatase are associated with troponin isolated from cardiac muscle. 3. Bovine cardiac 3':5'-cyclic AMP-dependent protein kinase catalyses the phosphorylation of cardiac troponin I 30 times faster than white-skeletal-muscle troponin I. 4. Troponin I is the only component of cardiac troponin phosphorylated at a significant rate by the endogenous or a bovine cardiac 3':5'-cyclic AMP-dependent protein kinase. 5. Phosphorylase kinase catalyses the phosphorylation of cardiac troponin I at similar or slightly faster rates than white-skeletal-muscle troponin I. 6. Troponin C inhibits the phosphorylation of cardiac and skeletal troponin I catalysed by phosphorylase kinase and the phosphorylation of white skeletal troponin I catalysed by 3':5'-cyclic AMP-dependent protein kinase; the phosphorylation of cardiac troponin I catalysed by the latter enzyme is not inhibited.

Animals↗
PubMed1974

Phosphorylation of troponin and the effects of interactions between the components of the complex.

1. The troponin complex from skeletal muscle contains approximately 1 mol of phosphate/80000g of complex, covalently bound to the troponin T component. 2. On prolonged incubation of the troponin complex or troponin T with phosphorylase kinase the phosphate content of troponin T was increased to approx. 3mol/mol. 3. On prolonged incubation of troponin I with phosphorylase kinase up to 1.6mol of phosphate/mol were incorporated. 4. Phosphorylation of troponin I was greatly inhibited by troponin C owing to the strong interaction between these proteins. Thus in the troponin complex troponin T was the main substrate for phosphorylase kinase. The phosphorylation of isolated troponin T was also inhibited by troponin C. 5. Troponin I was phosphorylated when the troponin complex was incubated with a bovine cardiac 3':5'-cyclic AMP-dependent protein kinase. Troponin T either in its isolated form or in the troponin complex was not phosphorylated by bovine protein kinase to any significant extent under the conditions used. 6. If the troponin complex was dephosphorylated to 0.2mol/mol, or phosphorylated up to 2.5mol/mol there was no significant effect on the ability of normal concentrations to confer Ca(2+) sensitivity on the adenosine triphosphatase of densensitized actomyosin.

Actomyosin↗
PubMed1973

Phosphorylation of the "37000 component" of the troponin complex (troponin-t).

Most of the phosphorus present in the troponin complex, which on average contains 1 mol of P/80000g, is associated with the ;37000 component' (0.6mol of P/mol). The inhibitory protein and particularly the ;37000 component', but not the calcium-binding protein, were phosphorylated when incubated with phosphorylase b kinase and [gamma-(32)P]ATP.

Animals↗
PubMed1972

The regulatory proteins of the myofibril. Separation and biological activity of the components of inhibitory-factor preparations.

1. Inhibitory-factor preparations isolated from myofibrils were shown to consist principally of proteins with molecular weights of 37000 and 23000. Under certain preparative procedures an additional component of molecular weight 14000 was present. 2. The 23000-dalton protein, the inhibitory factor, was the major active component. Its activity was enhanced by tropomyosin. 3. The 14000-dalton component also possessed inhibitory activity, although less than that of the 23000-dalton component when compared on a molar basis. Its activity was not always enhanced by tropomyosin. The 14000-dalton component could not be detected in whole fresh myofibrils and the limited evidence available is compatible with its formation during the preparation of the troponin complex. 4. The 37000-dalton component could not replace the inhibitory factor, calcium-sensitizing factor or tropomyosin as components of the relaxing-protein system. 5. All three components had distinctive amino acid compositions, particularly in their cysteine content.

Actomyosin↗
PubMed1969

Diphtheria toxin subunit active in vitro.

Exposure of diphtheria toxin to dithiothreitol (and similar thiols) resulted in a subunit which was active in catalyzing the adenosine diphosphateribosylation of mammalian aminoacyl-transferase II in the presence of nicotinamide adenine dinucleotide. At the same time there was a marked increase in total ADP-ribosylation activity. A molecule which was apparently identical to the derived subunit in size and activity was detected in partially purified preparations of toxin.

Adenine Nucleotides↗