ISSN:
1573-4919
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Summary Recent advances in the studies of the aggregation of G-actin monomers, containing one molecule of ATP, to long filaments of F-actin, with a concomitant hydrolysis of the nucleotide to ADP, are reviewed. With the aid of ε-ATP, the association and dissociation rate constant of the nucleotide could be determined. The binding of the nucleotide is enhanced by the binding of one Ca++ ion, probably at a different site. The ΔG value of the Mg++ or Ca++ induced polymerization has been determined to −39 to −59 kJ/mole, the critical protein concentration for the ATP-G-actin to ADP-F-actin conversion is very strongly influenced by the concentration of bivalent cations. The rate constants of the protein monomers, and the rate and equilibrium constants for the propagation step show the process to be extremely cooperative. Actin shows the interesting phenomenon of translocational head-to-tail polymerization, which may be regulated by ATP. The contact sites between the monomers in F-actin have been labeled by chemical modification. Two tryosine residues, 53 and 69, are probably close to one of the two sites. The ATP binding site has been labeled by an ATP analog, and there is evidence that it is close to the contact site.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00215273
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