Proteolytic removal of three C-terminal residues of actin alters the monomer-monomer interactions.
Homogeneous preparations of actin devoid of the three C-terminal residues were obtained by digestion of G-actin with trypsin after blocking proteolysis at other sites by substitution of Mg2+ for the tightly bound Ca2+. Removal of the C-terminal residues resulted in the following: an enhancement of the Mg(2+)-induced hydrolysis of ATP in low-ionic-strength solutions of actin; an increase in the critical concentration for polymerization; a decrease in the initial rate of polymerization; and an enhancement of the steady-state exchange of subunits in the polymer. Electron microscopy indicated an increased fragility of the filaments assembled from truncated actin. The results suggest that removal of the C-terminal residues increases the rate constants for monomer dissociation from the polymer ends and from the oligomeric species.
Mossakowska
M
M
Department of Muscle Biochemistry, Nencki Institute of Experimental Biology, Warsaw, Poland.
Moraczewska
J
J
Khaitlina
S
S
Strzelecka-Golaszewska
H
H
D000199:Actins / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D003545:Cysteine / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D046911:Macromolecular Substances; D008274:Magnesium / Q000378:metabolism; D009282:Naphthalenesulfonates / Q000378:metabolism; D010446:Peptide Fragments / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D011487:Protein Conformation; D011817:Rabbits; D012542:Scattering, Radiation; D013050:Spectrometry, Fluorescence; D013439:Sulfhydryl Reagents / Q000378:metabolism; D014357:Trypsin / Q000494:pharmacology
D000199:Actins; D005456:Fluorescent Dyes; D046911:Macromolecular Substances; D009282:Naphthalenesulfonates; D010446:Peptide Fragments; D013439:Sulfhydryl Reagents; D011189:Potassium Chloride; C006421:1,5-I-AEDANS; D000255:Adenosine Triphosphate; D014357:Trypsin; D008274:Magnesium; D003545:Cysteine