Inhibition of β(s)-chain dependent polymerization by synergistic complementation of contact site perturbations of α-chain: Application of semisynthetic chimeric α-chains

Sonati Srinivasulu, Ashok Malavalli, Muthuchidambaran Prabhakaran, Ronald L. Nagel, A. Seetharama Acharya

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

Mouse α1-30-horse α31-141 chimeric α-chain, a semisynthetic super-inhibitory α-chain, inhibits β(s)-chain dependent polymerization better than both parent α-chains. Although contact site sequence differences are absent in the α1-30 region of the chimeric chain, the four sequence differences of the region α17-22 could induce perturbations of the side chains at α16, α20 and α23, the three contact sites of the region. A synergistic complementation of such contact site perturbation with that of horse α31-141 probably results in the super-inhibitory activity of the chimeric α-chain. The inhibitory contact site sequence differences, by themselves, could also exhibit similar synergistic complementation. Accordingly, the polymerization inhibitory activity of Hb Le-Lamentin (LM) mutation [His20(α)→Gln], a contact site sequence difference, engineered into human-horse chimeric α-chain has been investigated to map such a synergistic complementation. Gln20(α) has little effect on the O2 affinity of HbS, but in human-horse chimeric α-chain it reduces the O2 affinity slightly. In the chimeric α-chain, Gln20(cl) increased sensitivity of the ββ cleft for the DPG influence, reflecting a cross-talk between the α1β1 interface and ββ cleft in this semisynthetic chimeric HbS. In the human α-chain frame, the polymerization inhibitory activity of Gln20(α) is higher compared with horse α1-30, but lower than mouse α1-30. Gln20(α) synergistically complements the inhibitory propensity of horse α31-141. However, the inhibitory activity of LM-horse chimeric α-chain is still lower than that of mouse-horse chimeric α-chain. Therefore, perturbation of multiple contact sites in the α1-30 region of the mouse-horse chimeric α-chain and its linkage with the inhibitory propensity of horse α31-141 has been now invoked to explain the super-inhibitory activity of the chimeric α-chain. The 'linkage-map' of contact sites can serve as a blueprint for designing synergistic complementation of multiple contact sites into α-chains as a strategy for generating super-inhibitory antisickling hemoglobins for gene therapy of sickle cell disease.

Original languageEnglish (US)
Pages (from-to)1105-1111
Number of pages7
JournalProtein Engineering
Volume12
Issue number12
Publication statusPublished - Dec 1 1999

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Keywords

  • Chimeric HbS
  • HbS polymerization
  • Intermolecular contact sites
  • Linkage map
  • Protein engineering
  • Super-inhibitory α-chain

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology

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