XXXX residues at positions 234 and 236 in @entity375 porin are involved in its assembly into the mitochondrial outer membrane.

@entity71345 @entity2227 @entity4339 @entity71341 @entity12553 @entity71342 @entity71343 @entity376 @entity71340 @entity71344 @entity375
Various point mutations of @entity12553 residues in @entity375 mitochondrial porin (283 residues) were tested for their ability to assemble in vitro into the outer membranes of intact @entity375 mitochondria. Assembly was evaluated by protection from proteinases. The extent of assembly of two of the mutants, @entity71340 and @entity71341 porins, was much less than for wild-type in either post-translational or co-translational assembly assays. @entity376 to @entity2227 mutants at other positions and @entity71342 porin assembled as well as wild-type, but @entity71343 porin was poorly inserted. When both Lys-234 and Lys-236 were mutated, @entity71342 / @entity71344 porin was inserted better than @entity71343 / @entity71345 porin, which was inserted better than @entity71340 / @entity71341 ; however, none of these mutants assembled as well as wild-type porin. It was concluded that optimal assembly of @entity375 porin depended on the presence of positively charged residues at both positions 234 and 236 and a @entity376 at one of these positions. After undergoing the assembly reaction, mutants that were vulnerable to proteinase K (i.e. @entity71340 , @entity71343 , and @entity71341 porins) seemed to be incompletely digested and were, to varying degrees, resistant to extraction by @entity4339 (pH 11.5). These experiments suggested that these mutants were incompletely inserted into the outer membrane. Both Lys-234 and Lys-236 are included in an internal pentapeptide, VKAKV, that is conserved in porins from protists, plants, and animals, and it is possible that, at least, the lysines in this tract are one of the signals for the membrane assembly of these proteins.
