Inhibition of {beta}S-chain dependent polymerization by synergistic complementation of contact site perturbations of {alpha}-chain: application of semisynthetic chimeric {alpha}-chains |
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Authors: | Srinivasulu Sonati; Malavalli Ashok; Prabhakaran Muthuchidambaran; Nagel Ronald L; Acharya ASeetharama |
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Affiliation: | 1 Division of Hematology, Department of Medicine and
2 Department of Physiology and Biophysics, Albert Einstein College of Medicine, 1300, Morris Park Avenue, Bronx, NY 10461 and
3 Structural Bioinformatics, San Diego, CA 92127, USA |
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Abstract: | Mouse 130-horse 31141 chimeric -chain, a semisyntheticsuper-inhibitory -chain, inhibits ßS-chain dependent polymerizationbetter than both parent -chains. Although contact site sequencedifferences are absent in the 130 region of the chimericchain, the four sequence differences of the region 17-22 couldinduce perturbations of the side chains at 16, 20 and 23, thethree contact sites of the region. A synergistic complementationof such contact site perturbation with that of horse 31141probably results in the super-inhibitory activity of the chimeric -chain. The inhibitory contact site sequence differences, bythemselves, could also exhibit similar synergistic complementation.Accordingly, the polymerization inhibitory activity of Hb Le-Lamentin(LM) mutation His20( ) Gln], a contact site sequence difference,engineered into humanhorse chimeric -chain has been investigatedto map such a synergistic complementation. Gln20( ) has littleeffect on the O2 affinity of HbS, but in humanhorse chimeric -chain it reduces the O2 affinity slightly. In the chimeric -chain, Gln20( ) increased sensitivity of the ßßcleft for the DPG influence, reflecting a cross-talk betweenthe 1ß1 interface and ßß cleft in this semisyntheticchimeric HbS. In the human -chain frame, the polymerizationinhibitory activity of Gln20( ) is higher compared with horse 130, but lower than mouse 130. Gln20( ) synergisticallycomplements the inhibitory propensity of horse 31141.However, the inhibitory activity of LMhorse chimeric -chain is still lower than that of mousehorse chimeric -chain. Therefore, perturbation of multiple contact sites inthe 130 region of the mousehorse chimeric -chainand its linkage with the inhibitory propensity of horse 31141has been now invoked to explain the super-inhibitory activityof the chimeric -chain. The `linkage-map' of contact sites canserve as a blueprint for designing synergistic complementationof multiple contact sites into -chains as a strategy for generatingsuper-inhibitory antisickling hemoglobins for gene therapy ofsickle cell disease. |
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Keywords: | chimeric HbS/ HbS polymerization/ intermolecular contact sites/ linkage map/ protein engineering/ super-inhibitory -chain" target="_blank">gif" ALT="{alpha}" BORDER="0">-chain |
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