Functional analysis of the Tsh autotransporter from an avian pathogenic Escherichia coli strain.
The temperature-sensitive hemagglutinin (Tsh) is an autotransporter protein secreted by avian-pathogenic Escherichia coli strains that colonize the respiratory tract and lead to airsacculitis, pericarditis, and colisepticemia. It is synthesized as a 140-kDa precursor protein, whose processing results in a 106-kDa passenger domain (Tshs) and a 33-kDa beta-domain (Tsh(beta)). The presence of a conserved 7-amino-acid serine protease motif within Tshs classifies the protein in a subfamily of autotransporters, known as serine protease autotransporters of the Enterobacteriaceae. In this study, we report that purified Tshs is capable of adhering to red blood cells, hemoglobin, and the extracellular matrix proteins fibronectin and collagen IV. We also demonstrate that Tshs exerts proteolytic activity against casein, and we provide experimental evidence demonstrating that serine 259 is essential for the protease function. However, this residue is not required for adherence to substrates, and its replacement by an alanine does not abolish binding activity. In summary, our results demonstrate that Tsh is a bifunctional protein with both adhesive and proteolytic properties.
Kostakioti
Maria
M
Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204, USA.
Stathopoulos
Christos
C
D018830:Adhesins, Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D001717:Birds / Q000382:microbiology*; D002364:Caseins / Q000378:metabolism; D024141:Collagen Type IV / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D006388:Hemagglutinins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism; D011485:Protein Binding; D012694:Serine / Q000235:genetics / Q000378:metabolism; D012697:Serine Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013696:Temperature
D018830:Adhesins, Escherichia coli; D002364:Caseins; D024141:Collagen Type IV; D005353:Fibronectins; D006388:Hemagglutinins; D006454:Hemoglobins; C112027:tsh protein, E coli; D012694:Serine; D012697:Serine Endopeptidases