Structural studies of haemoglobin from pisces species shortfin mako shark (Isurus oxyrinchus)at 1.9 Å resolution

Abstract

Haemoglobin (Hb) is a tetrameric iron-containing protein that carries oxygen from the lungs to tissues and carbon dioxide from tissues back to the lungs. Pisces are the advanced aquatic vertebrates capable of surviving at wide depth ranges. The shortfin mako shark (SMS) is the pelagic, largest, fastest and most sophisticated species of the shark kingdom with well developed eyes. Mostly the pisces species are cold blooded in nature. Distinctly, the SMSs are warmblooded animals with an advanced circulatory system. SMSs are capable of maintaining elevated muscle temperatures up to 33 K above the ambient water temperatures at a depth of 150-500 m. SMSs have a diverged air-breathing mechanism compared with other vertebrates. The haemoglobin molecule consists of four polypeptide chains, namely two chains, each with 140 amino acids and two chains each having 136 amino acids. The SMS Hb was found to crystallize in monoclinic space group P2 1 using the hanging-drop vapourdiffusion method at room temperature. The crystal packing parameters for the SMS Hb structure contain one whole biological molecule in the asymmetric unit with a solvent content of 47%. The SMS Hb quaternary structural features interface-interface interactions and heme binding sites are discussed with different state Hbs and the results reveal that SMS Hb adopts an unliganded deoxy T state conformation.

Crystal structure of hemoglobin from mouse (Mus musculus) compared with those from other small animals and humans

“…Mouse Hb was purified using previously reported procedures (Sundaresan et al, 2009;Ramesh et al, 2013). In brief, fresh blood collected from mice was mixed with 10%(w/v) ethylenediaminetetraacetic acid (EDTA) to avoid clotting.…”

Response toComments on Structural studies of haemoglobin from pisces species shortfin mako shark (Isurus oxyrinchus) at 1.9 Å resolution by P. Rameshet al.(2013).J. Synchrotron Rad.20, 843–847

“…The following is a response to the points raised in the comment by Merlino et al on our recent paper on haemoglobin (Hb) from the shortfin mako shark (SMS) (Ramesh et al, 2013).…”

“…With regard to those two states, our SMS Hb belongs to the deoxy T state conformation, and we confirmed that there is no ligand in the heme binding pocket, such as CO and O 2 , in SMS Hb. We therefore concluded that SMS Hb belongs to the deoxy unliganded T state conformation (Ramesh et al, 2013). We first purified native protein from shark blood and then performed the crystallization directly.…”

“…The maps showed that the chain does not contain a water molecule but there is a water molecule in the case of the chain [see Figs. 4(a) and 4(b), respectively, of Ramesh et al (2013)]. If a water molecule is present in both chains, we can say that Hb belongs to the aquomet form.…”

Comments onStructural studies of haemoglobin from pisces species shortfin mako shark (Isurus oxyrinchus) at 1.9 Å resolutionby P. Rameshet al.(2013).J. Synchrotron Rad.20, 843–847

“…The recent paper by Ramesh et al (2013) reports a crystallographic study on the tetrameric haemoglobin (Hb) isolated from the shortfin mako shark (Isurus oxyrinchus) (SMS). From the analysis of the overall and local features of the model the authors conclude that the structure corresponds to an unliganded deoxy T state conformation.…”