title: Transition of environmental polarity of tyrosine-76 of Trimeresurus flavoviridis phospholipase A2 upon active site ligand binding.
abstract: Modification of Trimeresurus flavoviridis phospholipase A2 with a 5-fold molar excess of tetranitromethane produced 40% active mononitrotyrosyl phospholipase A2 in which Tyr-76 was specifically nitrated. This is in contrast to the case of mammalian pancreatic phospholipases A2 where Tyr-70 but not Tyr-76 was nitrated. When Ca2+ was bound to T. flavoviridis mononitrotyrosyl phospholipase A2, nitrated tyrosine (Tyr(NO2))-76 moved from a less polar site to a polar site with the decrease of the pKa value of its hydroxyl group. Nitration of Tyr-76 did not influence the binding affinity to Ca2+. Addition of laurylphosphorylcholine to mononitrotyrosyl phospholipase A2 in the presence of Ca2+ caused the movement of Tyr(NO2)-76 from a polar environment to a less polar environment with the rise in the pKa value. Tyrosine-76 is located in the site whose environmental polarity is affected by the binding of the ligands to the active site. As Tyr-76 is located in the site not proximal to the active site, it could be assumed that the conformational change induced by the binding of the ligands extends to the region remote from the active site in T. flavoviridis phospholipase A2. This might provide evidence of long-range diffusional coupling between remote sites in the noncooperative globular protein.
authors.affiliation: Laboratory of Enzyme Chemistry, Faculty of Science, Kyushu University, Fukuoka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Sakai
authors.forename: N
authors.initials: N
authors.lastname: Oda
authors.forename: T
authors.initials: T
authors.lastname: Kohzuma
authors.forename: S Y
authors.initials: SY
authors.lastname: Liu
authors.forename: M
authors.initials: M
authors.lastname: Ohno
authors.forename: H
authors.initials: H
authors.lastname: Kihara
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002118:Calcium; D002417:Cattle; D003435:Crotalid Venoms; D008969:Molecular Sequence Data; D010179:Pancreas / Q000201:enzymology; D010740:Phospholipases / Q000378:metabolism*; D010741:Phospholipases A / Q000302:isolation & purification / Q000378:metabolism*; D054467:Phospholipases A2; D010767:Phosphorylcholine / Q000031:analogs & derivatives; D012689:Sequence Homology, Nucleic Acid; D013053:Spectrophotometry; D013057:Spectrum Analysis; D013774:Tetranitromethane; D014443:Tyrosine / Q000378:metabolism
chemical_list: D000596:Amino Acids; D003435:Crotalid Venoms; C029748:Trimeresurus venoms; D010767:Phosphorylcholine; D014443:Tyrosine; C028810:dodecylphosphocholine; D010740:Phospholipases; D010741:Phospholipases A; D054467:Phospholipases A2; D013774:Tetranitromethane; D002118:Calcium