Denaturation of MM-creatine kinase by sodium dodecyl sulfate.
The denaturation of dimeric cytoplasmic MM-creatine kinase by sodium dodecyl sulfate (SDS) has been investigated using activity measurements, far-ultraviolet circular dichroism, SEC-HPLC, electric birefringence, intrinsic probes (cysteine and tryptophan residues), and an extrinsic fluorescent probe (ANS). Our results show that inactivation is the first detectable event; the inactivation curve midpoint is located around 0.9 mM SDS. The second event is dissociation and it occurs in parallel to tertiary and secondary perturbations, as demonstrated by the coincidence (near 1.3 mM) of the midpoints of the transition curves monitoring dissociation and structural changes. At high total SDS concentration (concentration higher than 2.5 mM), the monomer had bound 170 mol of SDS per mol of protein. In these conditions, electric birefringence experiments suggest that the SDS-CK complex may be described as a prolate ellipsoid with an axial ratio of 1.27 (14 nm x 11 nm). These results are compatible with recent models of SDS-protein complexes: the "protein decorated micelle structure" or the "necklace structure".
Couthon
F
F
Biomembranes et enzymes associés, URA 1535 CNRS, Université Claude Bernard Lyon I, Villeurbanne, France.
Clottes
E
E
Angrand
M
M
Roux
B
B
Vial
C
C
D000817:Anilino Naphthalenesulfonates; D002942:Circular Dichroism; D003402:Creatine Kinase / Q000737:chemistry*; D007527:Isoenzymes; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
D000817:Anilino Naphthalenesulfonates; D007527:Isoenzymes; D012967:Sodium Dodecyl Sulfate; C027132:1-anilino-8-naphthalenesulfonate; D003402:Creatine Kinase