Structural properties of 2/2 hemoglobins: The group III protein from Helicobacter hepaticus

• Published in: IUBMB life Vol. 63; no. 3; pp. 197 - 205
• Main Authors: Nothnagel, Henry J., Winer, Benjamin Y., Vuletich, David A., Pond, Matthew P., Lecomte, Juliette T. J.
• Format: Journal Article
• Language: English
• Published: New York Wiley Subscription Services, Inc., a Wiley company 01-03-2011; Wiley Subscription Services, Inc
• Subjects: Amino Acid Sequence; Campylobacter jejuni; Helicobacter hepaticus; Helicobacter hepaticus - chemistry; Hemoglobins - chemistry; Models, Molecular; Molecular Sequence Data; Nuclear Magnetic Resonance, Biomolecular; paramagnetic NMR; Protein Conformation; self‐association; Sequence Homology, Amino Acid; trHbP; truncated Hb
• ISSN: 1521-6543; 1521-6551
• DOI: 10.1002/iub.430

The ε‐proteobacterium Helicobacter hepaticus (Hh) contains a gene coding for a hemoglobin (Hb). The protein belongs to the 2/2 Hb lineage and is representative of group III, a set of Hbs about which little is known. An expression and purification procedure was developed for Hh Hb. Electronic absorption and nuclear magnetic resonance (NMR) spectra were used to characterize ligation states of the ferric and ferrous protein. The pKa of the acid/alkaline transition of ferric Hh Hb was 7.3, an unusually low value. NMR analysis of the cyanomet complex showed the orientation of the heme group to be reversed when compared with most group I and group II 2/2 Hbs. Ferrous Hh Hb formed a stable cyanide complex that yielded NMR spectra similar to those of the carbonmonoxy complex. All forms of Hh Hb were self‐associated at NMR concentrations. Comparison was made to the related Campylobacter jejuni 2/2 Hb (Ctb), and the amino acid conservation pattern of group III was reinspected to help in the generalization of structure–function relationships. © 2011 IUBMB IUBMB Life, 63(3): 197–205, 2011