title: Regulation of the type IV secretion ATPase TrwD by magnesium: implications for catalytic mechanism of the secretion ATPase superfamily.
abstract: TrwD, the VirB11 homologue in conjugative plasmid R388, is a member of the large secretion ATPase superfamily, which includes ATPases from bacterial type II and type IV secretion systems, type IV pilus, and archaeal flagellae assembly. Based on structural studies of the VirB11 homologues in Helicobacter pylori and Brucella suis and the archaeal type II secretion ATPase GspE, a unified mechanism for the secretion ATPase superfamily has been proposed. Here, we have found that the ATP turnover of TrwD is down-regulated by physiological concentrations of magnesium. This regulation is exerted by increasing the affinity for ADP, hence delaying product release. Circular dichroism and limited proteolysis analysis indicate that magnesium induces conformational changes in the protein that promote a more rigid, but less active, form of the enzyme. The results shown here provide new insights into the catalytic mechanism of the secretion ATPase superfamily.
authors.affiliation: Departamento de Biología Molecular, Universidad de Cantabria (UC) e Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC (CSIC-UC-IDICAN), 39011 Santander.
authors.forename: Jorge
authors.initials: J
authors.lastname: Ripoll-Rozada
authors.affiliation: Departamento de Biología Molecular, Universidad de Cantabria (UC) e Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC (CSIC-UC-IDICAN), 39011 Santander.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Peña
authors.affiliation: Unidad de Biofísica (CSIC-UPV/EH) y Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, Apartado 644, 48080 Bilbao, Spain.
authors.forename: Susana
authors.initials: S
authors.lastname: Rivas
authors.affiliation: Unidad de Biofísica (CSIC-UPV/EH) y Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, Apartado 644, 48080 Bilbao, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Moro
authors.affiliation: Departamento de Biología Molecular, Universidad de Cantabria (UC) e Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC (CSIC-UC-IDICAN), 39011 Santander.
authors.forename: Fernando
authors.initials: F
authors.lastname: de la Cruz
authors.affiliation: Departamento de Biología Molecular, Universidad de Cantabria (UC) e Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC (CSIC-UC-IDICAN), 39011 Santander. Electronic address: cabezone@unican.es.
authors.forename: Elena
authors.initials: E
authors.lastname: Cabezón
authors.affiliation: Departamento de Biología Molecular, Universidad de Cantabria (UC) e Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC (CSIC-UC-IDICAN), 39011 Santander. Electronic address: arechagai@unican.es.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Arechaga
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D058947:Bacterial Secretion Systems / Q000502:physiology*; D041021:Brucella suis / Q000201:enzymology* / Q000235:genetics; D016480:Helicobacter pylori / Q000201:enzymology* / Q000235:genetics; D010957:Plasmids / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D000251:Adenosine Triphosphatases