Crystallization and X-ray diffraction analysis of a novel surface-adhesin protein: protein E fromHaemophilus influenzae

Abstract

Protein E (PE) is a ubiquitous multifunctional surface protein ofHaemophilusspp. and other bacterial pathogens of thePasteurellaceaefamily.H. influenzaeutilizes PE for attachment to respiratory epithelial cells. In addition, PE interacts directly with plasminogen and the extracellular matrix (ECM) components vitronectin and laminin. Vitronectin is a complement regulator that inhibits the formation of the membrane-attack complex (MAC). PE-mediated vitronectin recruitment at theH. influenzaesurface thus inhibits MAC and protects against serum bactericidal activity. Laminin is an abundant ECM protein and is present in the basement membrane that helps in adherence of H. influenzaeduring colonization. Here, the expression, purification and crystallization of and the collection of high-resolution data for this importantH. influenzaeadhesin are reported. To solve the phase problem for PE, Met residues were introduced and an SeMet variant was expressed and crystallized. Both native and SeMet-containing PE gave plate-like crystals in space groupP21, with unit-cell parametersa= 44,b= 57,c= 61 Å, β = 96°. Diffraction data collected from native and SeMet-derivative crystals extended to resolutions of 1.8 and 2.6 Å, respectively.