The topology of SH3-fold. The sequential numbering of strands from B1 to B5 could be seen with the connecting loops as RT, n-src, distal. The last loop which was equivalent to omega loop was a short 310-helix in majority of SH3-fold proteins. Although the connectivity of RT-loop was different in OB-fold and SH3-fold, the physical position of RT-loop was approximately equivalent. This figure was made as figure 1.