Structural, Functional and Conformational Properties of Rat Hemoglobins

Abstract

The oxygen equilibrium properties of rat total hemoglobin show pH dependence. Thus oxygen affinity and cooperativity, which are significantly reduced at pH 6.0, show increase with increasing pH. Conformational studies using nitrosyl derivatives indicate that in rat nitrosyl hemoglobin the R to T equilibrium is shiftcd towards the T state in going from pH 7.0 to pH 6.0. Under similar conditions human hemoglobin A shows no significant changes in cooperativity or conformation. These results indicate that a destabilized oxy structure (R) exist in rat hemoglobins at pH 6.0. Alterations in the heme pockets and a1 p2 contact points could Icad to these structural characteristics. Crystallization of rat hemoglobins is dependent on an oxy-like structure since all liganded ferrous derivatives and methemoglobin form crystals in the pH range of 7.0-8.0. Deoxygenation of oxyhemoglobin crystals or addition of inositol hexakisphosphate to nitrosyl or methemoglobin derivatives result in the solubilization of the crystals. Thus the quaternary and/or tertiary structural changes involved in the transition of an R to T state disrupt the crystal structure. The precise positioning of the complementary sites involved in the interaction of amino acids between rat hemoglobin tetramers seems to occur only when the molecules are in the quaternary or tertiary R conformation. This is in contrast to the polymerization 01' human deoxyhemoglobin S, where gel formation occurs only in the T state.

Infectious blood source alters early foregut infection and regurgitative transmission of Yersinia pestis by rodent fleas

“…These crystals were not observed in the digestive tract of infected fleas that fed on mouse or gerbil blood ( Fig 3C, 3D, 3G and 3H ). The morphology and color of these crystals were identical to descriptions of oxyhemoglobin crystals of the rat (rhomboidal or trapezoidal) and guinea pig (pyramidal) [ 31 , 32 ]. Most of the rat hemoglobin crystals in the flea guts formed rhomboids, but some were jagged and trapezoidal.…”

Transfusion of Old RBCs Induces Neuroinflammation and Cognitive Impairment

“…We used human hemoglobin because we could not find a source to purchase rat hemoglobin. In addition, rat hemoglobin is similar to human hemoglobin (29). Finally, results from human hemoglobin may be clinically relevant.…”

Metabolism of Bis(4-fluorobenzyl)trisulfide and Its Formation of Hemoglobin Adduct in Rat Erythrocytes

“…Cys125 is the obvious target because it is located externally at the a1/b1 interface of Hb (John, 1982). The exposure level of Cys125 dmd.aspetjournals.org to solvent is the highest one among the 5 cysteine residues, thus the steric hindrance for the reaction of BFBTS with Cys125 was negligible.…”

“…The prevalence of Cys125-modified peptides on b chain revealed that Cys125 was the most reactive site in rat Hb toward BFBTS, which was also consistent with the previous report defining the Cys125 on rat Hb b chain as the fast reacting thiol . Cys104/111 on a chain is located internally at the a1/b1 interface (John, 1982); it was suggested that the dissociation of tetramers into dimers will give access to Cys104/111. Cys13 was buried in a chain and Cys93 on b chain was also less exposed to solvent than Cys125, both of which were defined as low-reactive thiol residues.…”