López Cuevas, Yahaira

Profile Picture

Filters

20071
Reset filters

Settings

Citations

Publication Search Results

Now showing 1 - 1 of 1
  • Thumbnail Image
    Publication
    The role of position E11 in the stabilization of the HbI-SH2 complex from L. pectinata
    (2007) López Cuevas, Yahaira; López Garriga, Juan; College of Arts and Sciences - Sciences; Vera Colón, Marisol; Cortés Figueroa, José E.; Department of Chemistry; Cardona Martínez, Nelson
    The bivalve mollusk, Lucina pectinata, contains three hemoglobins: hemoglobin I (HbI) which is a H2S reactive protein, hemoglobin II (HbII) and hemoglobin III (HbIII) which deliver O2 to the organism. HbI is a monomeric protein that contains an unusual distal pocket characterized by the presence of a GlnE7 and aromatic residues PheB10 PheE11and PheCD1 that stabilize ligands such as H2S. Substitution of the GlnE7 residue by Val, Asp, His and PheB10 by Leu or Tyr demonstrated that both residues at the E7 and B10 positions are crucial for the H2S reactivity towards HbI. Mutations at the position E11 by Val, Tyr and Gln residues in presence of H2S ligand were analyzed to determine the association rate constant value (kon) and the dissociation rate constant value (koff), respectively. To determine the association and dissociation rate constants two different techniques were used: (i) Stopped flow (association rate constants) and (ii) UVVIS spectrophotometry (dissociation rate constants). The values obtained for the association constant values for the PheE11 substitution for Val, Tyr and Gln were 1.33 x 104 M-1 s -1, 1.04 x 104 M-1 s -1 and 2.6 x 104 M-1 s -1, respectively. Dissociation rate constants obtained for the Val, Tyr and Gln substitution were 3.199 x 10-5 s -1, 1.683 x 10-5 s -1 and 9.2 x 10-5 s -1, respectively. Results demonstrated that PheE11 is not a gate pathway for entrance or exit of the H2S ligand. However, this position influences synergistically the role of other heme pocket amino acids such as GlnE7 and PheB10, to move towards or away the ligand-binding site. Data also suggests that E11 position has no a direct influence in the heme-ligand association constant while indirectly affects the heme-ligand dissociation constant.