title: Unusual CO bonding geometry in abnormal subunits of hemoglobin M Boston and hemoglobin M Saskatoon.
abstract: To clarify the role of the proximal histidine (F8-His), distal His (E7-His), and E11 valine (E11-Val) in ligand binding of hemoglobin (Hb), we have investigated the resonance Raman (RR) spectra of the carbon monoxide adduct of Hbs M (COHb M) in which one of these residues was genetically replaced by another amino acid in either the alpha or beta subunit. In the fully reduced state, all Hbs M gave v3 at approximately 1472 cm-1 and vFe-His at 214-218 cm-1, indicating that they have a pentacoordinate heme and the heme iron is bound to either E7-His or F8-His. The porphyrin skeletal vibrations of the COHb M were essentially unaltered by replacements of E7- or F8-His with tyrosine (Tyr) and of E11-Val by glutamic acid (Glu). The vCO, vFe-CO, and delta Fe-C-O frequencies of COHb M Iwate (alpha F8-His----Tyr), COHb M Hyde Park (beta F8-His----Tyr), and COHb M Milwaukee (beta E11-Val----Glu) were nearly identical with those of COHb A. In contrast, the RR spectra of COHb M Boston (alpha E7-His----Tyr) and COHb M Saskatoon (beta E7-His----Tyr) gave two new Raman bands derived from the abnormal subunits, vFe-CO at 490 cm-1 and vCO at 1972 cm-1, in addition to those from the normal subunits at 505 cm-1 (vFe-CO) and 1952 cm-1 (vCO). The CO adduct of the abnormal subunits exhibited apparently no photodissociation upon illumination of CW laser with a stationary cell under which the normal subunit exhibited complete photodissociation.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Biological Laboratory, Kanazawa University School of Allied Medical Professions, Ishikawa, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nagai
authors.forename: Y
authors.initials: Y
authors.lastname: Yoneyama
authors.forename: T
authors.initials: T
authors.lastname: Kitagawa
mesh_terms: D001665:Binding Sites; D002248:Carbon Monoxide / Q000097:blood*; D002263:Carboxyhemoglobin / Q000378:metabolism*; D006441:Hemoglobin A / Q000378:metabolism; D006449:Hemoglobin M / Q000302:isolation & purification / Q000378:metabolism*; D006455:Hemoglobins, Abnormal / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D010108:Oxyhemoglobins / Q000378:metabolism; D011487:Protein Conformation; D013053:Spectrophotometry; D013059:Spectrum Analysis, Raman
chemical_list: D006455:Hemoglobins, Abnormal; D010108:Oxyhemoglobins; C027541:hemoglobin M Boston; C028907:hemoglobin Saskatoon; D002248:Carbon Monoxide; D006441:Hemoglobin A; D002263:Carboxyhemoglobin; D006449:Hemoglobin M