title: Structure of liganded T-state haemoglobin from cat (Felis silvestris catus), a low oxygen-affinity species, in two different crystal forms.
abstract: Haemoglobin (Hb) is an iron-containing metalloprotein which plays a major role in the transportation of oxygen from the lungs to tissues and of carbon dioxide back to the lungs. Hb is in equilibrium between low-affinity tense (T) and high-affinity relaxed (R) states associated with its unliganded and liganded forms, respectively. Mammalian species can be classified into two groups on the basis of whether they express `high' or `low' oxygen-affinity Hbs. Although Hbs from the former group have been studied extensively, a more limited number of structural studies have been performed for low oxygen-affinity Hbs. Here, the crystal structure of low oxygen-affinity cat methaemoglobin (metHb) has been solved at 2.0 and 2.4 Å resolution in two different crystal forms. Even though both structures are fully liganded, they unusually adopt a T-state-like quaternary conformation but with several localized R-like tertiary-structural and quaternary-structural features. The study provides atomic-level insights into the ligand-binding properties of this Hb, including its low cooperativity, blunt response to allosteric effectors and low affinity for oxygen, as well as further contributing to the mechanism underlying Hb allostery.
authors.affiliation: Centre of Advanced Study in Crystallography and Biophysics, University of Madras, Guindy Campus, Chennai 600 025, India.
authors.forename: Moovarkumudalvan
authors.initials: M
authors.lastname: Balasubramanian
authors.affiliation: Centre of Advanced Study in Crystallography and Biophysics, University of Madras, Guindy Campus, Chennai 600 025, India.
authors.forename: Ponnuraj
authors.initials: P
authors.lastname: Sathya Moorthy
authors.affiliation: Centre of Advanced Study in Crystallography and Biophysics, University of Madras, Guindy Campus, Chennai 600 025, India.
authors.forename: Kamariah
authors.initials: K
authors.lastname: Neelagandan
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 639798, Singapore.
authors.forename: Ramya
authors.initials: R
authors.lastname: Ramadoss
authors.affiliation: Qatar Biomedical Research Institute, Qatar Foundation, PO Box 5825, Doha, Qatar.
authors.forename: Prasanna R
authors.initials: PR
authors.lastname: Kolatkar
authors.affiliation: Centre of Advanced Study in Crystallography and Biophysics, University of Madras, Guindy Campus, Chennai 600 025, India.
authors.forename: M N
authors.initials: MN
authors.lastname: Ponnuswamy
mesh_terms: D000818:Animals; D002415:Cats; D003460:Crystallization; D019281:Dimerization; D006454:Hemoglobins / Q000737:chemistry*; D008024:Ligands; D010100:Oxygen / Q000737:chemistry*; D011487:Protein Conformation
chemical_list: D006454:Hemoglobins; D008024:Ligands; D010100:Oxygen
keywords: 2,3-diphosphoglycerate; Felis silvestris catus; allosteric mechanism; cat; cooperativity; haemoglobin; liganded T-state; low oxygen affinity