From the article,\" Elephantids are a particularly good model system to investig

Question

From the article," Elephantids are a particularly good model system to investigate the effects of memhers. Specifically, the group evolved in warm subtemperate climates, where extant Asian and African lineages are still found, with the ancestors of the extinct woolly mammoth (Mammuthus primigenius) abruptly invading high- latitude environments of Eurasia near the start of the Pleistocene ice ages some 1.2-2.0 llion years ago. Consistent with this environmental diaspora, the functional properties of woolly mammoth Hb were found to differ substantially from those of Asian elephant Hb, with the most notable change being a significant reduction in the overall H of the mammoth protein in the presence of naturally occurring allosteric effector molecules Interestingly, this functional shift comes about despite the fact that the primary sequences of Asian elephant Hb differ from those of the mammoth at enly one positioninthe -globin chain (KSN) and at threep lton (TI 2A, A8GS, and E 101 Q) in the -type globin chain, respectively (Table 1)a Of these latter residues, /612Ala of the mammoth protein is near the 2.3-bisphosphoglycerate (BPG) binding cleft, /086Ser is in the heme pocket, and /d101 Gln is located between 99Asp and 102Asn of the same chain in the intersubunit 1(6/6): interface, which are all critical to the function of Hb."

Explanation / Answer

Asp99 makes a hydrogen bond in the alpha1-beta2 interface between beta2-Asp99 and alpha1-Tyr42 that stabilizes, so T state is lost. Thus the R-T equilibrium is shifted toward the R state.

Asn102 makes a hydrogen bond in the alpha1-beta2 interface between beta2-Asn102 and alpha1-Asp94 that stabilizes, soR state is lost. Thus the R-T equilibrium is shifted toward the T state.

whwre as R state high O2 binding affinity and T state low O2 binding affinty.

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