Eur. Phys. J. E (2005) 16: 373-379
https://doi.org/10.1140/epje/i2004-10092-2

Haem conformation of amphibian nytrosylhaemoglobins detected by XANES spectroscopy

¹ Dipartimento di Fisica, Università di Roma “La Sapienza” and INFM, P.le A. Moro 5, 00185, Roma, Italy
² Dipartimento di Scienze Biochimiche, Università di Roma “La Sapienza” and INFM, P.le A. Moro 5, 00185, Roma, Italy
³ Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, Svante Arrhenius väg 12, SE-106 91, Stockholm, Sweden
⁴ I.S.M.-CNR and INFM, Via del fosso del cavaliere 100, 00133, Roma, Italy

^* e-mail: a.congiu@caspur.it

Received: 25 May 2004
Accepted: 17 January 2005
Published online: 3 March 2005

Abstract

We investigated for the first time the haem stereochemistry in the nitrosylated derivative of two amphibian haemoglobins, Xenopus laevis and Ambystoma mexicanum, by means of X-ray absorption spectroscopy technique with the aim to explain the relationships between the active site structure and physiological function of these proteins, compared to that from humans. Our results show that while the Fe site local structure of human HbNO is modulated by an allosteric effector such as IHP shifting the T-R equilibrium towards the T-state, the Fe site local structure of amphibians HbNO is stabilized in a particularly tensed T-state also without IHP.