NMR structure of Desulfovibrio gigas rubredoxin: a model for studying protein stabilization by compatible solutes

Rubredoxins are small, soluble proteins that display a wide variation in th ermostability, despite having a high degree of sequence similarity. They al so vary in the extent to which they are stabilized by solutes such as digly cerol phosphate. Hence, they provide excellent models for studying the mech anisms of thermostabilization. Nuclear magnetic resonance (NMR) spectroscop y can be used to investigate interactions between molecules, as well as sub tle changes in conformation in solution, and also provides a means to measu re protein stability. The assignment of the proton NMR spectrum of the zinc rubredoxin from Desulfovibrio gigas is presented, together with its struct ure in solution. The stabilizing effect of diglycerol phosphate on rubredox in is demonstrated and assessed by determining selected amide proton exchan ge rates; diglycerol phosphate at 100 mM concentration caused an additional structural stabilization of 1.2 +/- 0.4 kJ/mol. The pattern of effects on the exchange rates is discussed in relation to the protein structure.