Abstract
Mycoplasma pneumoniae is a bacterial human pathogen that causes primary atypical pneumonia. M. pneumoniae motility and infectivity are mediated by the immunodominant proteins P1 and P40/P90, which form a transmembrane adhesion complex. Here we report the structure of P1, determined by X-ray crystallography and cryo-electron microscopy, and the X-ray structure of P40/P90. Contrary to what had been suggested, the binding site for sialic acid was found in P40/P90 and not in P1. Genetic and clinical variability concentrates on the N-terminal domain surfaces of P1 and P40/P90. Polyclonal antibodies generated against the mostly conserved C-terminal domain of P1 inhibited adhesion of M. pneumoniae, and serology assays with sera from infected patients were positive when tested against this C-terminal domain. P40/P90 also showed strong reactivity against human infected sera. The architectural elements determined for P1 and P40/P90 open new possibilities in vaccine development against M. pneumoniae infections.
Highlights
Mycoplasma pneumoniae is a bacterial human pathogen that causes primary atypical pneumonia
We report the structures of M. pneumoniae proteins P1 and P40/P90 and of complexes of P40/P90 bound to sialylated oligosaccharides
Since the identification of the critical role of P1 in M. pneumoniae cytoadherence, it has been accepted that this protein was responsible for binding to sialic acid oligosaccharides[11,12,13,14,45]
Summary
Mycoplasma pneumoniae is a bacterial human pathogen that causes primary atypical pneumonia. 6 x His tag pneumoniae to cells of the respiratory tract is mediated by a network of adhesins and cytoadherence accessory proteins[9,10] Within this network the 170 kDa protein P1 was identified as a major determinant for cytoadherence and gliding motility with antibodies against P1 preventing both adhesion and motility[9,10,11,12]. For about 40 years, P1 has been assumed to be responsible for binding to sialic acid oligosaccharide receptors from the host cells[13] Because all these relevant properties, P1 has been attracting attention since the late 1970s, it was soon recognized that accessory proteins were required for its functioning[14]. The information is considered pivotal for clarifying the motility, infectivity, and epidemics of M. pneumoniae
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