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. 2003 Jul 11;278(28):25816-24.
doi: 10.1074/jbc.M301903200. Epub 2003 May 6.

Type III protein translocase: HrcN is a peripheral ATPase that is activated by oligomerization

Charalambos Pozidis  1 , Aggeliki Chalkiadaki, Amalia Gomez-Serrano, Henning Stahlberg, Ian Brown, Anastasia P Tampakaki, Ariel Lustig, Giorgos Sianidis, Anastasia S Politou, Andreas Engel, Nickolas J Panopoulos, John Mansfield, Anthony P Pugsley, Spyridoula Karamanou, Anastassios Economou
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Free article

Type III protein translocase: HrcN is a peripheral ATPase that is activated by oligomerization

Charalambos Pozidis et al. J Biol Chem. .
Free article

Abstract

Type III protein secretion (TTS) is catalyzed by translocases that span both membranes of Gram-negative bacteria. A hydrophilic TTS component homologous to F1/V1-ATPases is ubiquitous and essential for secretion. We show that hrcN encodes the putative TTS ATPase of Pseudomonas syringae pathovar phaseolicola and that HrcN is a peripheral protein that assembles in clusters at the membrane. A decahistidinyl HrcN derivative was overexpressed in Escherichia coli and purified to homogeneity in a folded state. Hydrodynamic analysis, cross-linking, and electron microscopy revealed four distinct HrcN forms: I, 48 kDa (monomer); II, approximately 300 kDa (putative hexamer); III, 575 kDa (dodecamer); and IV, approximately 3.5 MDa. Form III is the predominant form of HrcN at the membrane, and its ATPase activity is dramatically stimulated (>700-fold) over the basal activity of Form I. We propose that TTS ATPases catalyze protein translocation as activated homo-oligomers at the plasma membrane.

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