Morphology modifications in negatively charged lipid monolayers upon mitochondrial creatine kinase binding

Area of Science:

• Biochemistry
• Biophysics
• Cell Biology

Background:

• Mitochondrial creatine kinase (mtCK) is involved in cellular energy transfer.
• mtCK's potential role in mitochondrial membrane organization is not fully understood.
• Lipid-protein interactions are crucial for membrane structure and function.

Purpose of the Study:

• To investigate the effect of mtCK on the phase behavior of lipid monolayers.
• To determine if mtCK modulates lipid fluidity and organization.
• To explore the structural role of mtCK at the mitochondrial level.

Main Methods:

• Analysis of pressure-area isotherms for phosphatidylglycerol (PG) and cardiolipin monolayers.
• Measurement of compressional modulus variation with surface pressure.
• Visualization of monolayer morphology using Brewster angle microscopy.
• Observation of effects upon protein injection beneath monolayers.

Main Results:

• mtCK did not affect dimyristoylphosphatidylglycerol (DMPG) monolayers.
• mtCK facilitated the formation of a liquid condensed (LC) phase in dipalmitoylphosphatidylglycerol (DPPG) and distearoylphosphatidylglycerol (DSPG) monolayers.
• The effect of mtCK was more pronounced on tetramyristoylcardiolipin (TMCL) monolayers, inducing LC phase formation at lower surface pressures.
• mtCK induced and stabilized circular domains, indicating stabilization of the condensed phase.

Conclusions:

• mtCK can induce and stabilize a liquid condensed phase in specific lipid monolayers.
• These findings highlight a potential structural role for mtCK in mitochondrial membrane organization.
• Modulation of lipid phase behavior by mtCK may be significant for mitochondrial function.