Structural stability of adenylate kinase from the sulfate-reducing bacteria Desulfovibrio gigas

Biophysical Chemistry 110 (2004) 83–92

A novel adenylate kinase (AK) has recently been purified from Desulfovibrio gigas and characterized as a Co2+/Zn2+-containing enzyme: this is an unusual characteristic for AKs from Gram-negative bacteria, in which these enzymes are normally devoid of metals. Here, we studied the conformational stability of holo- and apo-AK as a function of temperature by differential scanning calorimetry (DSC), circular dichroism (CD), and intrinsic fluorescence spectroscopy. The thermal unfolding of AK is a cooperative two-state process, and is sufficiently reversible in the 9–11 pH range, that can be correctly interpreted in terms of a simple two-state thermodynamic model. The spectral parameters as monitored by ellipticity changes in the CD spectra of the enzyme as well as the decrease in tryptophan intensity emission upon heating were seen to be good complements to the highly sensitive but integral DSC-method.

supported in part by the Fundação para a Ciência e a Tecnologia, Portugal, fellowships BD/13775/97 to OYG, BPD/3518/00 to SAB, SFRH/BD/1067/2000 to DGP, and NATO Scientific Programme Fellowships for Spain, call 2002 to GGZ.