Illustration of distinct disulphide bond annotation in Ribonuclease A-like [SCOP family code: d.5.1.1] family of proteins. The structural alignment contains sixteen members. Marking of the disulphide bond positions on the structure based multiple sequence alignment has resulted in five distinct structural positions. However the maximum number of disulphides in a family member is only four, while the minimum is three. Each distinct disulphide bond is represented with approximate positions of their cysteines in the alignment. In the zoom out of the alignment region of the 4th distinct disulphide bond note the first cysteine is not in equivalent position, nevertheless it is conserved. Applying relaxation brings this disulphide bond into conservation. Also notice that this disulphide bond is not conserved in all the members.
Thangudu et al. BMC Structural Biology 2008 8:55 doi:10.1186/1472-6807-8-55