TY - JOUR
T1 - Hydrogen bonding of tyrosine B10 to heme-bound oxygen in Ascaris hemoglobin
T2 - Direct evidence from UV resonance raman spectroscopy
AU - Huang, Shuocai
AU - Huang, Jerry
AU - Kloek, Andrew P.
AU - Goldberg, Daniel E.
AU - Friedman, Joel M.
PY - 1996/1/12
Y1 - 1996/1/12
N2 - The hemoglobin from Ascaris suum, a parasitic nematode, has a spontaneous dissociation rate for the dioxygen ligand that is 3 orders of magnitude less than for mammalian myoglobins or hemoglobins. In this hemoglobin, the distal histidine is replaced with a glutamine which is capable of forming a stabilizing hydrogen bond to the bound dioxygen. A single hydrogen bond from a glutamine is, under typical circumstances, not sufficient to account for the low off rate for oxygen. Several studies point to a second hydrogen bond to the heme-bound dioxygen originating from tyrosine B10 as the source of this unusual reactivity. In this study ultraviolet (UV) resonance Raman spectroscopy is used to directly observe the formation of this hydrogen bond upon oxygen binding. The study reveals that both oxygen and carbon monoxide induce similar conformational changes in the globin upon binding to the heme; however, in the case of oxygen, a strong hydrogen bond involving a tyrosine is also observed. Similar studies on the QE7L mutant of this Hb suggest that the glutamine plays a role in stabilizing a rigid tertiary structure associated with the distal heme pocket. This conformation maintains the tyrosine in an orientation conducive to hydrogen bond formation with a heme-bound dioxygen ligand.
AB - The hemoglobin from Ascaris suum, a parasitic nematode, has a spontaneous dissociation rate for the dioxygen ligand that is 3 orders of magnitude less than for mammalian myoglobins or hemoglobins. In this hemoglobin, the distal histidine is replaced with a glutamine which is capable of forming a stabilizing hydrogen bond to the bound dioxygen. A single hydrogen bond from a glutamine is, under typical circumstances, not sufficient to account for the low off rate for oxygen. Several studies point to a second hydrogen bond to the heme-bound dioxygen originating from tyrosine B10 as the source of this unusual reactivity. In this study ultraviolet (UV) resonance Raman spectroscopy is used to directly observe the formation of this hydrogen bond upon oxygen binding. The study reveals that both oxygen and carbon monoxide induce similar conformational changes in the globin upon binding to the heme; however, in the case of oxygen, a strong hydrogen bond involving a tyrosine is also observed. Similar studies on the QE7L mutant of this Hb suggest that the glutamine plays a role in stabilizing a rigid tertiary structure associated with the distal heme pocket. This conformation maintains the tyrosine in an orientation conducive to hydrogen bond formation with a heme-bound dioxygen ligand.
UR - http://www.scopus.com/inward/record.url?scp=0030046276&partnerID=8YFLogxK
U2 - 10.1074/jbc.271.2.958
DO - 10.1074/jbc.271.2.958
M3 - Article
C2 - 8557711
AN - SCOPUS:0030046276
SN - 0021-9258
VL - 271
SP - 958
EP - 962
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 2
ER -