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Abstract

Intimin and Invasin are well-characterised virulence factors of enterophathogenic Escherichia coli and yersiniae, respectively. These outer membrane proteins belong to a family of proteins whose extracellular domain is secreted through the outer membrane by a novel autotransport mechanism, termed type Ve secretion [1]. Compared to classical (type Va) autotransporters, Intimin and Invasin have an inverted topology, with the Cterminal passenger being exported through an N-terminal beta-barrel pore [2]. In addition, these proteins have a small N-terminal periplasmic domain. The periplasmic domain of Intimin contains a lysine motif (LysM) region found in many peptidoglycan-binding proteins, but this motif is lacking in Invasin. We show that the periplasmic domain of Intimin, but not the smaller domain of Invasin, binds to peptidoglycan sacculi. The binding is pH-dependent and occurs only under acidic conditions (pH ≤ 6.0) periplasmic domain mediates dimerisation. In contrast to peptidoglycan binding, dimer formation by the Intimin periplasmic domain is independent of pH. The Invasin periplasmic domain does not promote dimerisation under any of the tested conditions. We are currently performing experiments to determine the region(s) in the periplasmic domain responsible for peptidoglycan binding and dimerisation, testing the relevance for dimerisation and peptidoglycan binding for host cell adherence and pedestal formation.