Functional and structural studies of mitochondrial porin

Abstract

Mitochondrial porin is a voltage-gated, anion-selective channel that facilitates the diffusion of small hydrophilic molecules across the mitochondrial outer membrane. The "glycine-leucine-lysine" (GLK) motif of porin is highly conserved among different species even though overall sequence similarity is quite low. The GLK motif is thought to be part of the ATP binding site for porin. ATP binding is known to alter ion selectivity of 'N. crassa ' porin. The GLK motif of 'N. crassa' porin was changed to GLE through site-directed mutagenesis. Cross-linking studies with 32P-ATP indicate that the GLE mutant was able to bind ATP while electrophysiological measurements indicate that the GLE mutant is able to form a pore in lipid bilayers with altered ion selectivity. Several versions of a B-barrel structural model have been proposed for mitochondrial porin. To further refine these models, a series of mutant versions of the porin of 'Neurospora crassa' were generated. (Abstract shortened by UMI.)