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Biomedical subjects

M G Rossmann

Publications and source records attributed to M G Rossmann.

At least 217 records · Page 12Linked to original sources
PubMed1975

A comparison of the heme binding pocket in globins and cytochrome b5.

Of the 85 three-dimensionally characterized residues of cytochrome b5, 51 are found to be structurally and topologically equivalent to the globin fold. When these proteins have been superimposed, the heme irons are found to be less than 1.4 A separated and the heme normals are inclined by less than 9.5 degrees. The proximal histidine of the globins and two adjacent helices are equivalent to the sixth iron ligand and adjacent helices of cytochrome b5. Larger differences in structure are observed on the distal side of the heme, coincident with the most changeable part of the globin structures. The heme itself is rotated by 53 degrees about its normal but such a change is energetically minimal and conservative as the heme side groups are not directly involved in the function of the molecules. The beta-sheet of cytochrome b5 is inserted into a corresponding cavity of the globins forming an additional lining to the heme pocket. The roughly 50 residues missing at the carboxy end of the known cytochrome b5 fragment could correspond in part to the H helix in the globins. While it would seem probable that these similarities represent divergent evolution from a primordial heme-binding protein, the possibility of structural convergence to a functionally satisfactory protein cannot be excluded.

Amino Acid Sequence↗
PubMed1973

Structure-function relationships in lactate dehydrogenase.

The binding of coenzyme and substrate are considered in relation to the known primary and tertiary structure of lactate dehydrogenase (EC 1.1.1.27). The adenine binds in a hydrophobic crevice, and the two coenzyme phosphates are oriented by interactions with the protein. The positively charged guanidinium group of arginine 101 then folds over the negatively charged phosphates, collapsing the loop region over the active center and positioning the unreactive B side of the nicotinamide in a hydrophobic protein environment. Collapse of the loop also introduces various charged groups into the vicinity of the substrate binding site. The substrate is situated between histidine 195 and the C4 position on the nicotinamide ring, and is partially oriented by interactions between its carboxyl group and arginine 171. The spatial arrangements of these groups may provide the specificity for the L-isomer of lactate.

Amino Acid Sequence↗