Biochemical and structural studies of two tetrameric nucleoside 2′-deoxyribosyltransferases from psychrophilic and mesophilic bacteria: Insights into cold-adaptation

Nucleoside 2 '-deoxyribosyltransferases (NDTs) catalyze the cleavage of glycosidic bonds of 2 '-deoxynucleosides and the following transfer of the 2 '-deoxyribose moiety to acceptor nucleobases. Here, we report the crystal structures and biochemical properties of the first tetrameric NDTs: the type I NDT from the mesophilic bacteriu m Enterococcus faecalis V583 (EfPDT) and the type II NDT from the bacteriu m Desulfotalea psychrophila (DpNDT), the first psychrophilic NDT. This novel structural and biochemical data permitted an exhaustive comparative analysis aimed to shed light into the basis of the high global stability of the psychrophilic DpNDT, which has a higher melting temperature than EfPDT (58.5 degrees C versus 54.4 degrees C) or other mesophilic NDTs. DpNDT possesses a combination of unusual structural motifs not present neither i n EfPDT nor any other NDT that most probably contribute to its global stability, in particular, a large aliphatic isoleucine-leucine-valine (ILV) bundle accom-panied by a vicinal disulfide bridge and also an intersubunit disulfide bridge, the first described for an NDT. The functional and structural features ofDpNDT do not fit the standard features of psychrophilic enzymes, which lead us to consider the implication of (sub)cellular levels together with the protein level in the adaptation of enzy-matic activity to low temperatures.

Automated summary

The study reports the crystal structures and biochemical properties of two novel tetrameric NDTs, including the first psychrophilic NDT. Comparative analysis of the new structural and biochemical data reveals that DpNDT has unique structural motifs that likely contribute to its global stability, and its functional and structural features differ from standard psychrophilic enzymes.