Table 2.

Putative roles for residues that influence the cyclization of Asn1023

EspP residue	Equivalent Hbp residue	Essential for cleavage site conformation	Sterically constrain Asn1023	Electrostatically position the carboxamide group of Asn1023	Position the putative catalytic water and accept a proton	Increase electrophilicity of $C_{\mathit{Carb}}^{\mathit{Asn}1023}$. Stabilize the oxyanion intermediate.	Facilitate proton transfer to $N_{\mathit{Amid}}^{\mathit{Asn}1024}$	Effect of alanine substitution on EspP cleavage
Lys1027	Lys1104		√					Moderate delay 25
Arg1028	Arg1105	√	√					Abolishes cleavage 25
Arg1044	Arg1121		√	√				Severe delay 1
Asp1120	Asp1197	√		√	√			Abolishes cleavage 23
Lys1124	Lys1201			√				Severe delay 1
Glu1154	Glu1231			√	√			Severe delay 23
Glu1172	Glu1249			√	√	√	√	Severe delay 23

¹This study