Classification of protein-DNA complexes based on structural descriptors.

We attempt to classify protein-DNA complexes by using a set of 11 descriptors, mainly characterizing protein-DNA interactions, including the number of atomic contacts at major and minor grooves, conformational deviations from standard B- and A-DNA forms, widths of DNA grooves, GC content, specificity measures of direct and indirect readouts, and buried surface area at the complex interface. The cluster analyses were carried out for a unique set of 62 complexes including a variety of protein motifs, and 7 distinct clusters were revealed from the analyses. We found that some proteins with the same motif are classified into different clusters, whereas different proteins with distinct motifs are classified into the same cluster. These results suggest that the conventional motif-based classification of DNA binding proteins may not necessarily correspond to structural and functional properties of protein-DNA complexes, and that the present classification will help to identify common properties and rules that govern protein-DNA recognition.