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Regulatory properties of neuronal cdc2-like kinase (1995)

Qi, Zhong ; Tang, Damu ; Matsuura, Isao ; [et al.]

Springer

Molecular and cellular biochemistry 149-150 (1995), S. 35-39

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ISSN: 1573-4919

Keywords: neuronal cdc2-like kinase ; cdk5 ; regulatory subunit ; neurofilament proteins ; tau ; Alzheimer disease

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Abstract Neuronal cdc2-like kinase, nclk, is a heterodimer of cyclin dependent protein kinase 5, cdk5, and a 25 kDa subunit derived from a novel, neuron-specific, 35 kDa protein: p35. The characterization and regulation of nclk will be summarized in this minireview. The activity of nclk appears to be governed by highly complex regulatory mechanisms including protein-protien interaction, protein phosphorylation and isoforms. The histone H1 kinase activity of nclk is absolutely dependent of the interaction between the 25 kDa subunit and the catalytic subunit, cdk5. In addition, nclk interacts with other cellular proteins to form macromolecular complexes. The kinase activity of nclk is inhibitedin vitro by the phosphorylation reactions of a weel-like protein tyrosine kinase and a protein serine/threonine kinase from bovine thymus. Northern blot analysis has revealed the existence of two populations of p35 mRNA of 2 and 4 kb. A novel cDNA encoding a p35 homologous protein has been obtained from a human hippocampus library.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01076561

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Gly-238-Ser substitution changes the substrate specificity of the SHV class A β-lactamases (1991)

Lee, Ki-Young ; Hopkins, John D. ; Syvanen, Michael ; [et al.]

New York, NY : Wiley-Blackwell

Proteins: Structure, Function, and Genetics 11 (1991), S. 45-51

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ISSN: 0887-3585

Keywords: third generation cephalosporins ; cefotaxime resistance ; enzyme structure-function ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine

Notes: The SHV-type β-lactamase SHV-2A is related to SHV-1 by a Gly-238-Ser replacement. Strains carrying SHV-2A are resistant to the third generation cephems cefotaxime and ceftizoxime, whereas those that carry SHV-1 are sensitive to these drugs. We present a kinetic analysis of a SHV-1 and SHV-2A enzymes, with the goal of gaining insight into the role of residue 238 in hydrolyzing cefotaxime and ceftizoxime. SHV-2A shows altered kinetic properties for a number of other cephems that also have heterocyclic side chains at the amino position of the 7-aminocephalosporanic acid nucleus (R1 side chain), including a significantly higher kcat/Km than does SHV-1 for cephaloridine, cephalothin, and cefotiam. Two cephems with straight chain R1 substitutions, cephalosporin C and cephacetrile, are not hydrolyzed more efficiently by SHV-2A. These results indicate that the Ser-238-Gly substitution increases the affinity toward cephems with a heterocyclic ring in the R1 side chain. In addition, the data for ampicillin and benzylpenicillin show that addition of a nitrogen to the second carbon of the R1 side chain of a penem results in a lower kcat/Km for SHV-2A relative to SHV-1. These data strongly suggest that the previously proposed hydrogen bond formation between Ser-238 and the second carbon nitrogen of cefotaxime is not an important factor in hydrolysis by SHV-2A. We propose that the Gly-238 to Ser-238 replacement in SHV-2A has altered the hydrophobic pocket so that it can better accommodate cephems with bulky R1 side chains.

Additional Material: 3 Ill.