How bacterial ADP-ribosylating toxins recognize substrates.
ExoS and ExoT are bifunctional type III cytotoxins of Pseudomonas aeruginosa that contain an N-terminal RhoGAP domain and a C-terminal ADP-ribosylation domain. Although they share 76% amino acid identity, ExoS and ExoT ADP-ribosylate different substrates. Using protein modeling and site-directed mutagenesis, the regions of ExoS and ExoT that define substrate specificity were determined. Regions B (active site loop), C (ARTT motif) and E (PN loop) on ExoS are necessary and sufficient to recognize ExoS targets, whereas regions B, C and E on ExoT are necessary but not sufficient to recognize ExoT targets, such as the Crk proteins. A specific Crk recognition motif on ExoT was defined as region A (helix alpha1). The electrostatic properties of regions A, B, C and E define the substrate specificity of ExoS and ExoT and these interactions can explain how other bacterial ADP-ribosylating toxins recognize their unique substrates.
Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, USA.
Jianjun
J
Sun
Anthony W
AW
Maresso
Jung-Ja P
JJ
Kim
Joseph T
JT
Barbieri
D036002:ADP Ribose Transferases / Q000737:chemistry; D020727:ADP-Ribosylation Factors / Q000737:chemistry*; D000244:Adenosine Diphosphate / Q000737:chemistry; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001427:Bacterial Toxins / Q000737:chemistry*; D001665:Binding Sites; D016466:CHO Cells; D006224:Cricetinae; D020690:GTPase-Activating Proteins; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000494:pharmacology; D013379:Substrate Specificity; D014343:Trypan Blue / Q000494:pharmacology
D001427:Bacterial Toxins; C477521:ExoT protein, Pseudomonas aeruginosa; D020690:GTPase-Activating Proteins; D000246:Adenosine Diphosphate Ribose; D012965:Sodium Chloride; D000244:Adenosine Diphosphate; D036002:ADP Ribose Transferases; C444820:exoenzyme S; D020727:ADP-Ribosylation Factors; D014343:Trypan Blue