1H, 13C, and 15N backbone and side chain resonance assignments of thermophilic Geobacillus kaustophilus cyclophilin-A.

Cyclophilins catalyze the reversible peptidyl-prolyl isomerization of their substrates and are present across all kingdoms of life from humans to bacteria. Although numerous biological roles have now been discovered for cyclophilins, their function was initially ascribed to their chaperone-like activity in protein folding where they catalyze the often rate-limiting step of proline isomerization. This chaperone-like activity may be especially important under extreme conditions where cyclophilins are often over expressed, such as in tumors for human cyclophilins (Lee Archiv Pharm Res 33(2): 181-187, 2010), but also in organisms that thrive under extreme conditions, such as theromophilic bacteria. Moreover, the reversible nature of the peptidyl-prolyl isomerization reaction catalyzed by cyclophilins has allowed these enzymes to serve as model systems for probing the role of conformational changes during catalytic turnover (Eisenmesser et al. Science 295(5559): 1520-1523, 2002; Eisenmesser et al. Nature 438(7064): 117-121, 2005). Thus, we present here the resonance assignments of a thermophilic cyclophilin from Geobacillus kaustophilus derived from deep-sea sediment (Takami et al. Extremophiles 8(5): 351-356, 2004). This thermophilic cyclophilin may now be studied at a variety of temperatures to provide insight into the comparative structure, dynamics, and catalytic mechanism of cyclophilins.