Faculty Collaboration Database

Molecular heterogeneity of a type III cytotoxin, Pseudomonas aeruginosa exoenzyme S. Biochemistry 2003 Dec 09;42(48):14249-57

Date

12/04/2003

Pubmed ID

14640693

DOI

10.1021/bi035053i

Scopus ID

2-s2.0-0344629874 (requires institutional sign-in at Scopus site)   4 Citations

Abstract

Pseudomonas aeruginosa ExoS is a bifunctional type III cytotoxin. The N-terminus (residues 1-232) is a Rho GTPase activating protein (GAP) domain, while the C-terminus (residues 233-453) is a FAS-dependent ADP-ribosyltransferase domain that targets Ras and Ras-like GTPases. A membrane localization domain (residues 51-72) localizes ExoS to a perinuclear region within eukaryotic cells. Recent studies observed that ExoS is auto-ADP-ribosylated upon delivery into eukaryotic cells. Auto-ADP-ribosylated ExoS analyzed from eukaryotic cells displayed pI heterogeneity and prompted an analysis of this heterogeneity. Bacterial-associated ExoS and ExoS that had been secreted by P. aeruginosa also showed pI heterogeneity with five charge forms ranging in pI from 5.1 to 5.9. The pI heterogeneity of ExoS was independent of a mass change and thus represented molecular charge conformers. Urea was not required to observe the pI conformers of ExoS; it enhanced the resolution and formation of pI conformers during the focusing component of the analysis. ExoS(E381D), a mutant deficient in ADP-ribosyltransferase activity, isolated from cultured cells showed charge forms that migrated to a more acidic pI than type III secreted ExoS but more basic than auto-ADP-ribosylated ExoS. Incubation of cell lysates with Mn(2+) shifted the pI of ExoS(E381D) to a pI identical to secreted ExoS. This indicates that within the mammalian cells ExoS undergoes a negatively charged modification, in addition to auto-ADP-ribosylation observed for wild-type ExoS. ExoT, ExoU, and YopE also focus into multiple pI forms, suggesting that this is a common property of type III cytotoxins.

Author List

Maresso AW, Riese MJ, Barbieri JT

Author

Joseph T. Barbieri PhD Professor in the Microbiology and Immunology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

ADP Ribose Transferases
Animals
Bacterial Toxins
CHO Cells
Cholic Acids
Cricetinae
Culture Media
Cytotoxins
GTPase-Activating Proteins
Intracellular Fluid
Isoelectric Point
Molecular Weight
Peptide Fragments
Protein Denaturation
Protein Structure, Tertiary
Protein Transport
Pseudomonas aeruginosa
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
Urea