Involvement of a tyrosine residue in the ADP binding site of creatine kinase. A second-derivative UV-spectroscopy study.
Second-derivative spectroscopy was used to determine the percentage of tyrosine residues that are exposed to solvent in rabbit MM-creatine kinase. Six residues, among the ten present per monomer, are solvent-exposed. The presence of creatine in the incubation medium does not modify this value. However, this number is decreased by one when the enzyme is incubated with saturating concentrations of MgADP. A dissociation constant for MgADP can be estimated and the obtained value (0.085 mM) is comparable to the Km for this substrate. Thus, a tyrosine residue is located near the MgADP binding site or is masked during protein conformational change induced by adenyl nucleotide binding.
Leydier
C
C
Biomembranes et Enzymes Associés, UPRESA 5013 Centre National de la Recherche Scientifique-Université Lyon I., Villeurbanne, France.
Clottes
E
E
Couthon
F
F
Marcillat
O
O
Vial
C
C
D000244:Adenosine Diphosphate / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D003402:Creatine Kinase / Q000737:chemistry* / Q000378:metabolism; D019791:Guanidine; D006146:Guanidines / Q000494:pharmacology; D007700:Kinetics; D009132:Muscles / Q000201:enzymology; D011489:Protein Denaturation; D011817:Rabbits; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D014443:Tyrosine / Q000737:chemistry* / Q000378:metabolism
D006146:Guanidines; D014443:Tyrosine; D000244:Adenosine Diphosphate; D003402:Creatine Kinase; D019791:Guanidine