Properties of a microtubule-associated cofactor-independent protein kinase from pig brain

A protein kinase activity was identified in pig brain that co-purified with microtubules through repeated cycles of temperature-dependent assembly and disassembly. The microtubule-associated protein kinase (MTAK) phosphorylated histone H1; this activity was not stimulated by cyclic nucleotides. Ca2+ plus calmodulin, phospholipids or polyamines. MTAK did not phosphorylate synthetic peptides which are substrates for cyclic AMP-dependent protein kinase, cyclic GMP-dependent protein kinase. Ca2+/calmodulin-dependent protein kinase II, protein kinase C or casein kinase II. MTAK activity was inhibited by trifluoperazine [IC50 (median inhibitory concn.) = 600 microM] in a Ca2+-independent fashion. Ca2+ alone was inhibitory [IC50 = 4 mM). MTAK was not inhibited by heparin, a potent inhibitor of casein kinase II, nor a synthetic peptide inhibitor of cyclic AMP-dependent protein kinase. MTAK demonstrated a broad pH maximum (7.5-8.5) and an apparent Km for ATP of 45 microM. Mg2+ was required for enzyme activity and could not be replaced by Mn2+. MTAK phosphorylated serine and threonine residues on histone H1. MTAK is a unique cofactor-independent protein kinase that binds to microtubule structures.

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The role of protein kinase activation in the control of steroidogenesis by adrenocorticotrophic hormone in the adrenal cortex

Biochemical Journal ◽

10.1042/bj1360993 ◽

1973 ◽

Vol 136 (4) ◽

pp. 993-998 ◽

Cited By ~ 29

Author(s):

Malcolm C. Richardson ◽

Dennis Schulster

Keyword(s):

Protein Kinase ◽

Cyclic Amp ◽

Adrenal Cortex ◽

Kinase Activity ◽

Protein Kinase Activity ◽

Adrenocorticotrophic Hormone ◽

Dependent Protein Kinase ◽

Kinase Activation ◽

Protein Kinase Activation ◽

Dependent Protein

A method has been developed for investigation of the effect of adrenocorticotrophic hormone (ACTH) on the state of activation of a cyclic AMP-dependent protein kinase within cells of the adrenal cortex. Enzyme activity was measured in terms of the quantity of32P transferred from [γ-32P]ATP to histone under conditions in which bound cyclic AMP did not dissociate from the regulatory subunit of the protein kinase ACTH (1×10-2i.u./ml) caused a rapid and complete activation of the cyclic AMP-dependent protein kinase activity within 2min of hormone addition to the isolated cells. In response to a range of ACTH concentrations a sigmoid log dose–response curve for protein kinase activation was obtained, with half-maximal stimulation attained at about 1×10-3i.u./ml. However, some low doses of ACTH that elicited a marked (but submaximal) steroidogenic response failed to cause a clear stimulation of protein kinase activity in isolated adrenal cells. Theophylline (2mm) potentiated the effect of ACTH on protein kinase activity. The results implicate an important role for protein kinase in ACTH action on the adrenocortical cell.

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Effect of thyroliberin on the concentration of adenosine 3′:5′-phosphate and on the activity of adenosine 3′:5′-phosphate-dependent protein kinase in prolactin-producing cells in culture

Biochemical Journal ◽

10.1042/bj1620379 ◽

1977 ◽

Vol 162 (2) ◽

pp. 379-386 ◽

Cited By ~ 30

Author(s):

K M Gautvik ◽

E Walaas ◽

O Walaas

Keyword(s):

Protein Kinase ◽

Cyclic Amp ◽

Time Course ◽

Pituitary Tumour ◽

Enzyme Activation ◽

Protein Kinase Activity ◽

Half Maximum ◽

Prolactin Release ◽

Dependent Protein Kinase ◽

Dependent Protein

1. The effects of thyroliberin were studied in cultured rat pituitary-tumour cells that synthesize and secrete prolactin (the GH4C1 cell strain). 2. Prolactin and cyclic AMP were measured by radioimmunological methods, and a cyclic AMP-dependent protein kinase was characterized by using histone as substrate. 3. Prolactin release was studied after 5-60min of treatment, and synthesis after 48h of treatment with thyroliberin. One-half maximum stimulation of release and synthesis were observed at 0.25 and at 4nM respectively. 4. Cyclic AMP was temporarily increased in cell suspensions after treatment with thyroliberin, and one-half maximum stimulation was observed at 25nM. 5. Dibutyryl cyclic AMP increased prolactin release and synthesis, one-half maximum effects being obtained at 20 micronM. 6. A cyclic AMP-dependent protein kinase, which was one-half maximally stimulated at 30 nM-cyclic AMP, was demonstrated. 7. An increase in the activity ratio (-cyclic AMP/+cyclic AMP) of the cyclic AMP-dependent protein kinase was observed after treatment with thyroliberin. Total protein kinase activity in the presence of cyclic AMP was unaltered. The time-course of enzyme activation was similar to that of cyclic AMP formation and corresponded to the time when prolactin release was first observed. 8. It is concluded that thyroliberin induces cyclic AMP formation, resulting in the activation of a cyclic AMP-dependent protein kinase.

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The Saccharomyces cerevisiae SRK1 gene, a suppressor of bcy1 and ins1, may be involved in protein phosphatase function

Molecular and Cellular Biology ◽

10.1128/mcb.11.6.3369-3373.1991 ◽

1991 ◽

Vol 11 (6) ◽

pp. 3369-3373

Author(s):

R B Wilson ◽

A A Brenner ◽

T B White ◽

M J Engler ◽

J P Gaughran ◽

...

Keyword(s):

Saccharomyces Cerevisiae ◽

Protein Kinase ◽

Cyclic Amp ◽

Protein Phosphatase ◽

Shuttle Vector ◽

Temperature Sensitive ◽

Protein Kinase Activity ◽

Dependent Protein Kinase ◽

Cycle Arrest ◽

Dependent Protein

The Saccharomyces cerevisiae SRK1 gene, when expressed on a low-copy shuttle vector, partially suppresses the phenotype associated with elevated levels of cyclic AMP-dependent protein kinase activity and suppresses the temperature-sensitive cell cycle arrest of the ins1 mutant. SRK1 is located on chromosome IV, 3 centimorgans from gcn2. A mutant carrying a deletion mutation in srk1 is viable. SRK1 encodes a 140-kDa protein with homology to the dis3+ protein from Schizosaccharomyces pombe. The ability of SRK1 to alleviate partially the defects caused by high levels of cyclic AMP-dependent protein kinase and the similarity of its encoded protein to dis3+ suggest that SRK1 may have a role in protein phosphatase function.

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