Isolation and characterisation of the major outer membrane protein of Erwinia carotovora

The purified major outer membrane protein (37275 Da) from the psychrotrophic phytopathogen Erwinia carotovora MFCL0 was structurally characterised by MALDI-TOF mass spectrometry, N-terminal microsequencing and DNA sequence determinations, and secondary structure prediction analyses. The deduced amino acid sequence showed 76% and 72% of similarities with the Serratia marcescens and Escherichia coli OmpA proteins respectively. Dendrogram analysis allowed to point out that E. carotovora is close to the genus Serratia. After reconstitution into planar lipid bilayers, this major protein induced ion channels with a major conductance level of 630 pS in 1 M NaCl and a weak cationic selectivity. These functional and structural features allowed to identify this major outer membrane component of E. carotovora as an OmpA-like protein, i.e., a channel-forming protein which could be involved in the infection process of this phytopathogen agent.