A cis-proline in α-hemoglobin stabilizing protein directs the structural reorganization of α-hemoglobin

David A. Gell, Liang Feng, Suiping Zhou, Philip D. Jeffrey, Katerina Bendak, Andrew Gow, Mitchell J. Weiss, Yigong Shi, Joel P. Mackay

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Abstract

α-Hemoglobin (αHb) stabilizing protein (AHSP) is expressed in erythropoietic tissues as an accessory factor in hemoglobin synthesis. AHSP forms a specific complex with αHb and suppresses the heme-catalyzed evolution of reactive oxygen species by converting αHb to a conformation in which the heme is coordinated at both axial positions by histidine side chains (bis-histidyl coordination). Currently, the detailed mechanism by which AHSP induces structural changes in αHb has not been determined. Here, we present x-ray crystallography, NMR spectroscopy, and mutagenesis data that identify, for the first time, the importance of an evolutionarily conserved proline, Pro30, in loop 1 of AHSP. Mutation of Pro30 to a variety of residue types results in reduced ability to convert αHb. In complex with-Hb, AHSP Pro30 adopts a cis-peptidyl conformation and makes contact with the N terminus of helix G in αHb. Mutations that stabilize the cis-peptidyl conformation of free AHSP, also enhance the αHb conversion activity. These findings suggest that AHSP loop 1 can transmit structural changes to the heme pocket of αHb, and, more generally, highlight the importance of cis-peptidyl prolyl residues in defining the conformation of regulatory protein loops.

Original languageEnglish
Pages (from-to)29462-29469
Number of pages8
JournalJournal of Biological Chemistry
Volume284
Issue number43
DOIs
Publication statusPublished - 23 Oct 2009
Externally publishedYes

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ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

Cite this

Gell, D. A., Feng, L., Zhou, S., Jeffrey, P. D., Bendak, K., Gow, A., Weiss, M. J., Shi, Y., & Mackay, J. P. (2009). A cis-proline in α-hemoglobin stabilizing protein directs the structural reorganization of α-hemoglobin. Journal of Biological Chemistry, 284(43), 29462-29469. https://doi.org/10.1074/jbc.M109.027045