Characteristic of aromatic amino acid substitution at alpha 96 of hemoglobin.
Replacement of valine by tryptophan or tyrosine at position alpha96 of the alpha chain (alpha96Val), located in the alpha(1)beta(2) subunit interface of hemoglobin leads to low oxygen affinity hemoglobin, and has been suggested to be due to the extra stability introduced by an aromatic amino acid at the alpha96 position. The characteristic of aromatic amino acid substitution at the alpha96 of hemoglobin has been further investigated by producing double mutant r Hb (alpha42Tyr --> Phe, alpha96Val --> Trp). r Hb (alpha42Tyr --> Phe) is known to exhibit almost no cooperativity in binding oxygen, and possesses high oxygen affinity due to the disruption of the hydrogen bond between alpha42Tyr and beta99Asp in thealpha(1)beta(2) subunit interface of deoxy Hb A. The second mutation, alpha96Val -->Trp, may compensate the functional defects of r Hb (alpha42Tyr --> Phe), if the stability due to the introduction of trypophan at the alpha 96 position is strong enough to overcome the defect of r Hb (alpha42Tyr --> Phe). Double mutant r Hb (alpha42Tyr --> Phe, alpha96Val --> Trp) exhibited almost no cooperativity in binding oxygen and possessed high oxygen affinity, similarly to that of r Hb (alpha42Tyr --> Phe). (1)H NMR spectroscopic data of r Hb (alpha42Tyr --> Phe, alpha96Val --> Trp) also showed a very unstable deoxy-quaternary structure. The present investigation has demonstrated that the presence of the crucible hydrogen bond between alpha 42Tyr and beta 99Asp is essential for the novel oxygen binding properties of deoxy Hb (alpha96Val --> Trp) .
Choi
Jong-Whan
JW
Department of Biochemistry Wonju 220-701, Korea.
Lee
Jong Hyuk
JH
Lee
Kwang Ho
KH
Lee
Hyean-Woo
HW
Sohn
Joon Hyung
JH
Yoon
Joon Ho
JH
Yeh
Byung-Il
BI
Park
Seung Kyu
SK
Lee
Kyu Jae
KJ
Kim
Hyun-Won
HW
D019943:Amino Acid Substitution; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D009154:Mutation / Q000235:genetics*; D010100:Oxygen / Q000378:metabolism*; D010649:Phenylalanine / Q000737:chemistry; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000378:metabolism; D014364:Tryptophan / Q000737:chemistry*; D014443:Tyrosine / Q000737:chemistry*; D014633:Valine / Q000737:chemistry
D006454:Hemoglobins; D021122:Protein Subunits; D011994:Recombinant Proteins; D014443:Tyrosine; D010649:Phenylalanine; D014364:Tryptophan; D014633:Valine; D010100:Oxygen