Structure and Function of X-Pro Dipeptide Repeats in the TonB Proteins of Salmonella typhimurium and Escherichia coli - Brewer, S.; Tolley, M.; Trayer, I. P.; Barr, G. C.; Dorman, C. J.; Hannavy, K.; Higgins, C. F.; Evans, J. S.; Levine, B. A.; Wormald, M. R. (Biological Magnetic Resonance Bank, 1995)