Tail tubular protein A: a dual-function tail protein of Klebsiella pneumoniae bacteriophage KP32

Anna Pyra,Miroslawa Dauter,Andrzej Gamian,Ewa Brzozowska,Krzysztof Pawlik,Zbigniew Dauter

doi:10.1038/s41598-017-02451-3

Abstract

Tail tubular protein A (TTPA) is a structural tail protein of Klebsiella pneumoniae bacteriophage KP32, and is responsible for adhering the bacteriophage to host cells. For the first time, we found that TTPA also exhibits lytic activity towards capsular exopolysaccharide (EPS) of the multiresistant clinical strain of Klebsiella pneumoniae, PCM2713, and thus should be regarded as a dual-function macromolecule that exhibits both structural and enzymatic actions. Here, we present our crystallographic and enzymatic studies of TTPA. TTPA was crystallized and X-ray diffraction data were collected to a resolution of 1.9 Å. In the crystal, TTPA molecules were found to adopt a tetrameric structure with α-helical domains on one side and β-strands and loops on the other. The novel crystal structure of TTPA resembles those of the bacteriophage T7 tail protein gp11 and gp4 of bacteriophage P22, but TTPA contains an additional antiparallel β-sheet carrying a lectin-like domain that could be responsible for EPS binding. The enzymatic activity of TTPA may reflect the presence of a peptidoglycan hydrolase domain in the α-helical region (amino acid residues 126 to 173). These novel results provide new insights into the enzymatic mechanism through which TTPA acts on polysaccharides.

Highlights

The strains of Klebsiella pneumoniae belong to the Enterobacteriaceae family and are widely distributed in the environment[1]
Based on the observation that tail tubular protein A (TTPA) is active against K. pneumoniae – bacteria that are able to produce large amount of slime polysaccharides, we assessed the effect of TTPA on bacterial capsular polysaccharides
Our microscopic studies showed that K. pneumoniae cells treated with purified TTPA (10 μl 0.5 mg/ml) were denuded of their capsules, whereas control cells were surrounded by capsules (Fig. 2B)

Summary

Introduction

The strains of Klebsiella pneumoniae belong to the Enterobacteriaceae family and are widely distributed in the environment[1]. A biofilm is an organized structure in which bacterial cells stick to one another on various solid surfaces, forming large aggregates[9]. One of the major biofilm adhesion factors is a bacterial polysaccharide that is secreted outside the cell, and is called exopolysaccharide (EPS)[10]. Depolymerases are present as part of the phage tail or are secreted outside the cell as a separate enzyme. This process facilitates bacterial infection and produces translucent halos around the clear phage plaques on a bacterial lawn[18]. The phage depolymerases are expected to be diverse, as they act on a wide variety of EPSs. The KP32 bacteriophage belongs to the Caudovirales family and can infect multidrug resistant K. pneumoniae isolates[20]. We describe the first results relating to these proteins, namely crystallographic and functional studies of TTPA

Methods

Results

Conclusion