Conformational stability of neuroglobin helix F - Possible effects on the folding pathway within the globin family

Luca Codutti, Paola Picotti, Oriano Marin, Sylvia Dewilde, Federico Fogolari, Alessandra Corazza, Paolo Viglino, Luc Moens, Gennaro Esposito, Angelo Fontana

Research output: Contribution to journalArticlepeer-review

Abstract

Neuroglobin is a recently discovered member of the globin family, mainly observed in neurons and retina. Despite the low sequence identity (less than 20% over the whole sequence for the human proteins), the general fold of neuroglobin closely resembles that of myoglobin. The latter is a paradigmatic protein for folding studies, whereas much less is known about the neuroglobin folding pathway. In this work, we show how the structural features of helix F in neuroglobin and myoglobin could represent a pivotal difference in their folding pathways. Former studies widely documented that myoglobin lacks helix F in the apo form. In this study, limited proteolysis experiments on aponeuroglobin showed that helix F does not undergo proteolytic cleavage, suggesting that, also in the apo form, this helix maintains a rigid and structured conformation. To understand better the structural properties of helices F in the two proteins, we analyzed peptides encompassing helix F of neuroglobin and myoglobin in the wild-type and mutant forms. NMR and CD experiments revealed a helical conformation for neuroglobin helix F peptide, at both pH 7 and pH 2, absent in the myoglobin peptide. In particular, NMR data suggest a secondary structure stabilization effect caused by hydrophobic interactions involving Tyr88, Leu89 and Leu92. Molecular dynamics simulations performed on the apo and holo forms of the two proteins reveal the persistence of helix F in neuroglobin even in the absence of heme. Conversely myoglobin shows a higher mobility of the N-terminus of helix F on heme removal, which leads to the loss of secondary structure.

Original languageEnglish (US)
Pages (from-to)5177-5190
Number of pages14
JournalFEBS Journal
Volume276
Issue number18
DOIs
StatePublished - Sep 2009

Keywords

  • Circular dichroism
  • Globin folding
  • Myoglobin
  • NMR
  • Neuroglobin

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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