A New Unstable, High Oxygen Affinity Hemoglobin: Hb Nagoya Or β97 (Fg4) His→Pro

Abstract

An unstable hemoglobin was detected by isopropanol and heat precipitation tests in a 49-year-old Japanese man suffering from acute exacerbation of a chronic hemolytic disorder which was apparently triggered by infection of cholelithiasis. One of his two sons carried the same abnormal hemoglobin, and was jaundiced, but otherwise healthy, without anemia. The abnormal hemoglobin focused at a slightly more anodic position than Hb A in thin layer polyacrylamide gel electrofocusing. The abnormal beta chain emerged after normal beta chain in reverse phase high performance liquid chromatography of the hemolysate. It comprised 16.7% and 25.5% of the total beta chain in the propositus and his son, respectively. The partially heme-depleted abnormal beta subunit was precipitated with p-chloromercuribenzoic acid, and the abnormal beta chain was isolated by urea CM-cellulose column chromatography. Structural analysis demonstrated substitution of proline for histidine at position 97 (FG4) in the beta chain. The abnormal hemoglobin was purified by ion-exchange column chromatography. It showed a hyperbolic oxygen equilibrium curve indicating a high oxygen affinity and the absence of cooperative intersubunit interaction. Subunit dissociation seemed to be slightly enhanced. The variant was markedly susceptible to oxidation and rapidly lost heme upon oxidation.

Hb Malmö [β-97(FG-4)His→Gln] leading to polycythemia in a Dutch family

“…In Hb Malmö and also in the other three hemoglobin variants described at position b-97, i.e., Hb Wood (His]Leu) [25], Hb Nagoya (His]Pro) [18], and Hb Moriguchi (His]Tyr) [19], the substitutions disrupt the intra-helix contact of the conserved histidine, which is probably essential for maintenance of the right shape of the b-FG p-helix. The stability of this helix, which is the closing gate of the heme pocket, is maintained in the deoxy state by several molecular contacts (Table 2): the H-bonds between Asp b2-99, Tyr a 1 -42 and Asn a 1 -97; the heme-linking F9 histidine residue at position b-92; the H-bond between the CuO group of val b 2 -98 main chain and the Tyr b 2 -145 residue, whose side chain is also a a 1 /b 2 interface contact with Thr a 1 -41.…”

Haemoglobin Köln as de novo mutations in Sweden: Diagnosis by PCR and specific enzymatic cleavage

“…Other unstable variants such as Hb Nagoya, Hb Nottingham and Hb Djelfa will also give the same pattern, as will some stable variants, Hb Wood and Hb Malmd, as well as some putative variants that have not yet been described in the literature (23). Hb Wood, Hb Nagoya and Hb Malmd all appear as anodal variants upon isoelectric focusing (18,19,7). Hence, when the Mae I1 RFLP is used in combination with isoelectric focusing, only Hb Nottingham and possibly Hb Djelfa is at risk of being misdiagnosed as Hb Koln.…”

The role of amino acid α38 in the control of oxygen binding to human adult and embryonic haemoglobin Portland

“…A relatively large number of naturally occurring point mutations of the α " β # interface residues have been characterized. All of the mutants involving residues α%", α%% and β*( show increased oxygen affinity and reduced cooperativity [4][5][6][7][8][9]. The residue at position α$) by comparison is totally conserved in all adult mammalian species [10].…”