Two forms of @entity9305 have been identified, associated with the outer membrane of liver mitochondria (OM cyt b(5)) and with the membrane of the endoplasmic reticulum (microsomal, Mc cyt b(5)). These proteins have very similar structures, but differ significantly in physical properties, with the OM cyt b(5) exhibiting a more negative reduction potential, higher stability, and stronger interactions with the @entity1446 . We perform molecular dynamics simulations to probe the structures and fluctuations of the two proteins in solution, to help explain the observed physical differences. We find that the structures of the two proteins, highly similar in the crystal, differ in position of a surface loop involving residues 49-51 in solution. Hydrophobic residues Ala-18, Ile-32, Leu-36, and Leu-47 tend to cluster together on the surface of @entity35 OM cyt b(5), blocking water access to the protein interior. In @entity291 Mc cyt b(5), two of these positions, Ser-18 and @entity534 -47, are occupied by hydrophilic residues. This leads to breaking the hydrophobic cluster and allowing the protein to occupy a more open conformation. A measure of this structural transition is the opening of a cleft on the protein surface, which is 5 A wider in the OM cyt b(5) simulation compared to the Mc form. The OM protein also appears to have a more compact hydrophobic core in its beta-sheet region. These effects may be used to explain observed stability differences between the two proteins.

Molecular dynamics simulation studies of XXXX from outer mitochondrial and microsomal membrane.

@entity9305 :: ('64001(Tax:10116)', 'Gene') :: ['cytochrome b(5)'] @entity534 :: ('CHEBI:16467', 'Chemical') :: ['Arg'] @entity35 :: ('10116', 'Species') :: ['rat'] @entity291 :: ('9913', 'Species') :: ['bovine'] @entity1446 :: ('MESH:D006418', 'Chemical') :: ['heme']
@entity9305 :: (64001(Tax:10116),Gene) :: ['cytochrome b5']
