- The non-penicillin-binding module of the tripartite penicillin-binding protein 3 of Escherichia coli is required for folding and/or stability of the penicillin-binding module and the membrane-anchoring module confers cell septation activity on the folded structure. Goffin, C., Fraipont, C., Ayala, J., Terrak, M., Nguyen-Distèche, M., Ghuysen, J.M. J. Bacteriol. (1996)