Mitochondrial creatine kinase binding to phospholipid monolayers induces cardiolipin segregation.
It is well established that the octameric mitochondrial form of creatine kinase (mtCK) binds to the outer face of the inner mitochondrial membrane mainly via electrostatic interactions with cardiolipin (CL). However, little is known about the consequences of these interactions on membrane and protein levels. Brewster angle microscopy investigations provide, for the first time to our knowledge, images indicating that mtCK binding induced cluster formation on CL monolayers. The thickness of the clusters (10-12 nm) corresponds to the theoretical height of the mtCK-CL complex. Protein insertion into a condensed CL film, together with monolayer stabilization after protein addition, was observed by means of differential capacity measurements. Polarization modulation infrared reflection-absorption spectroscopy showed that the mean orientation of alpha-helices within the protein shifted upon CL binding from 30 degrees to 45 degrees with respect to the interface plane, demonstrating protein domain movements. A comparison of data obtained with CL and phosphatidylcholine/phosphatidylethanolamine/CL (2:1:1) monolayers indicates that mtCK is able to selectively recruit CL molecules within the mixed monolayer, consolidating and changing the morphology of the interfacial film. Therefore, CL-rich domains induced by mtCK binding could modulate mitochondrial inner membrane morphology into a raft-like organization and influence essential steps of mitochondria-mediated apoptosis.
Maniti
Ofelia
O
Chemistry-Biochemistry, Université de Lyon, Lyon, France.
Lecompte
Marie-France
MF
Marcillat
Olivier
O
Desbat
Bernard
B
Buchet
René
R
Vial
Christian
C
Granjon
Thierry
T
D000818:Animals; D002308:Cardiolipins / Q000737:chemistry / Q000378:metabolism*; D052281:Creatine Kinase, Mitochondrial Form / Q000737:chemistry / Q000378:metabolism*; D004566:Electrodes; D021962:Membrane Microdomains; D008567:Membranes, Artificial; D008853:Microscopy; D051336:Mitochondrial Membranes / Q000378:metabolism; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D011487:Protein Conformation; D011817:Rabbits; D013055:Spectrophotometry, Infrared
D002308:Cardiolipins; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; C483858:phosphatidylethanolamine; D052281:Creatine Kinase, Mitochondrial Form