Journal of Biological Physics

, Volume 31, Issue 3–4, pp 417–432

A Spectroscopic Study of Structural Heterogeneity and Carbon Monoxide Binding in Neuroglobin

Article

DOI: 10.1007/s10867-005-0173-0

Cite this article as:
Nienhaus, K. & Nienhaus, G.U. J Biol Phys (2005) 31: 417. doi:10.1007/s10867-005-0173-0

Abstract

Neuroglobin (Ngb) is a small globular protein that binds diatomic ligands like oxygen, carbon monoxide (CO) and nitric oxide at a heme prosthetic group. We have performed FTIR spectroscopy in the infrared stretching bands of CO and flash photolysis with monitoring in the electronic heme absorption bands to investigate structural heterogeneity at the active site of Ngb and its effects on CO binding and migration at cryogenic temperatures. Four CO stretching bands were identified; they correspond to discrete conformations that differ in structural details and CO binding properties. Based on a comparison of bound-state and photoproduct IR spectra of the wild-type protein, Ngb distal pocket mutants and myoglobin, we have provided structural interpretations of the conformations associated with the different CO bands. We have also studied ligand migration to the primary docking site, B. Rebinding from this site is governed by very low enthalpy barriers (∼1 kJ/mol), indicating an extremely reactive heme iron. Moreover, we have observed ligand migration to a secondary docking site, C, from which CO rebinding involves higher enthalpy barriers.

Key words

FTIR spectroscopy ligand binding neuroglobin temperature derivative spectroscopy 

Copyright information

© Springer Science + Business Media, Inc. 2005

Authors and Affiliations

  1. 1.Department of BiophysicsUniversity of UlmUlmGermany
  2. 2.Department of PhysicsUniversity of Illinois at Urbana-ChampaignUrbanaU.S.A.

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