Structure of human R-state aquomethemoglobin at 2.0?A resolution.

ABSTRACT: The crystal structure of tetrameric (??)(2) R-state human adult aquomethemoglobin is reported at 2.0?Å resolution. The asymmetric unit contained one ?? subunit pair. The R-state crystal belonged to space group P4(1)2(1)2, with unit-cell parameters a = b = 53.6, c = 192.8?Å. An Fe-bound water molecule was modeled into the heme distal pockets of each of the ? and ? subunits. In the ? subunit, a highly ordered liganded water was modeled with an Fe-O(water) distance of 2.2?Å and appears to be protected against escape from the distal pocket by the conformation of the heme propionate groups, which point upwards towards the distal His58 residue aided by a hydrogen-bonding network involving the solvent. In the ? subunit, the liganded water exhibited greater motion and was modeled with a longer Fe-O(water) distance of 2.5?Å; in this subunit both propionate groups point downwards away from the distal His63 residue, presumably allowing greater motion of the liganded water in and out of the distal pocket.

SUBMITTER: Yi J 

PROVIDER: S-EPMC3107133 | biostudies-literature | 2011 Jun

REPOSITORIES: biostudies-literature