Crystallization and preliminary X-ray diffraction studies of mutants of B1IgG-binding domain of protein L from Peptostreptococcus magnus

The small 62-residue IgG-binding domain B1 of protein L from Peptostreptoco ccus magnus (Ppl-B1) has proven to be a simple system for the study of the thermodynamics and kinetics of protein folding. X-ray diffraction studies h ave been initiated in order to determine how the thermostability, folding a nd unfolding rates of a series of point mutations spanning Ppl-B1 correlate with the high-resolution structures. To this end, a tryptophan-containing variant of Ppl-B1 (herein known as wild type) and two mutants, Lys61Ala and Val49Ala, have been crystallized. Full data sets have been collected for t he wild type and the Lys61Ala and Val49Ala mutants to resolutions of 1.7, 2 .3 and 1.8 Angstrom, respectively. interestingly all three crystallize usin g different precipitants and in different space groups. This may be a conse quence of the relatively large effects of single-site mutations on surface- charge distribution or structural conformation, which might affect crystal contact sites.