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Mutation of residue Phe97 to Leu disrupts the central allosteric pathway in Scapharca dimeric hemoglobin. (Articolo in rivista)

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Mutation of residue Phe97 to Leu disrupts the central allosteric pathway in Scapharca dimeric hemoglobin. (Articolo in rivista) (literal)

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Pardanani A, Gibson QH, Colotti G, Royer WE Jr. (1997)
Mutation of residue Phe97 to Leu disrupts the central allosteric pathway in Scapharca dimeric hemoglobin.
in The Journal of biological chemistry (Print); AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, BETHESDA (Stati Uniti d'America)
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UNIV MASSACHUSETTS,MED CTR,PROGRAM MOL MED,WORCESTER,MA 01605 UNIV MASSACHUSETTS,MED CTR,DEPT BIOCHEM & MOL BIOL,WORCESTER,MA 01605 CORNELL UNIV,DEPT BIOCHEM MOL & CELL BIOL,ITHACA,NY 1485 UNIV TEXAS,DEPT BIOCHEM & MOL BIOL,HOUSTON,TX 77025 UNIV ROMA LA SAPIENZA, CNR,CTR MOL BIOL,DEPT BIOCHEM SCI,I-00185 ROME,ITALY (literal)

Titolo

Mutation of residue Phe97 to Leu disrupts the central allosteric pathway in Scapharca dimeric hemoglobin. (literal)

Abstract

Residue Phe(97), which is thought to play a central role in the cooperative functioning of Scapharca dimeric hemoglobin, has been mutated to leucine to test its proposed role in mediating cooperative oxygen binding. This results in an 8-fold increase in oxygen affinity and a marked decrease in cooperativity, Kinetic measurements of ligand binding to the Leu(97) mutant suggest an altered unliganded (deoxy) state, which has been confirmed by high resolution crystal structures in the unliganded and carbon monoxide-liganded states, Analysis of the structures at allosteric end points reveals them to be remarkably similar to the corresponding wild-type structures, with differences confined to the disposition of residue 97 side chain, F-helix geometry, and the interface water structure, Increased oxygen affinity results from the absence of the Phe(97) side chain, whose tight packing in the heme pocket of the deoxy state normally restricts the heme from assuming a high affinity conformation, The absence of the Phe(97) side chain is also associated with diminished cooperativity, since Leu(97) packs in the heme pocket in both states, Residual cooperativity appears to be coupled with observed structural transitions and suggests that parallel pathways for communication exist in Scapharca dimeric hemoglobin. (literal)

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