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Title: Recognition and discrimination of gases by the oxygen-sensing signal transducer protein HemAT as revealed by FTIR spectroscopy
Authors: Pinakoulaki, Eftychia 
Yoshimura, Hideaki 
Varotsis, Constantinos 
Keywords: Fourier transform infrared spectroscopy;Hydrogen bonding;Molecular structure;Oxygen;Proteins;Transducers;Heme;Amino acid sequence
Issue Date: 2006
Publisher: ACS Publications
Source: Biochemistry, 2006, Volume 45, Issue 25, Pages 7763-7766
Abstract: The determination of ligand binding properties is a key step in our understanding of gas sensing and discrimination by gas sensory proteins. HemAT is a newly discovered signal transducer heme protein that recognizes O 2 and discriminates against other gases such as CO and NO. We have used FTIR spectroscopy on CO- and NO-bound sensor domain HemAT and sensor domain distal mutants Y70F, T95A, R91A, and L92A to gain insight into the structure of the iron-bound ligand at ambient temperature. These mutations were designed to perturb the electrostatic field near the iron-bound gaseous ligand and also allow us to investigate the communication pathway between the distal residues of the protein and the heme. We show the formation of both H-bonded and non-H-bonded conformations in the CO-bound forms. In addition, we report the presence of multiple conformations in the NO-bound forms. Such distal H-bonding is crucial for ligand binding and activation by the heme. The comparison of the O2, NO, and CO data demonstrates that Thr95 and Tyr70 are crucial for ligand recognition and discrimination and, thus, for specific sensing of gases, and L92 is crucial for controlling the conformational changes of the Thr95 and Tyr70 residues upon NO binding
ISSN: 00062960
DOI: 10.1021/bi0604072
Rights: © 2006 American Chemical Society
Type: Article
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