Peptidyl-prolyl cis-trans isomerases (PPT) catalyze cis-trans isomerization
of imide bonds in peptides and proteins. This review summarizes the litera
ture on the structure and functions of PPIs, their involvement in protein f
olding, and organization of PPI-containing receptors and membrane channels.
A possible role of several PPIs in distant interactions between cells is d
iscussed.