- PDZ domains facilitate binding of high temperature requirement protease A (HtrA) and tail-specific protease (Tsp) to heterologous substrates through recognition of the small stable RNA A (ssrA)-encoded peptide. Spiers, A., Lamb, H.K., Cocklin, S., Wheeler, K.A., Budworth, J., Dodds, A.L., Pallen, M.J., Maskell, D.J., Charles, I.G., Hawkins, A.R. J. Biol. Chem. (2002)