Tài liệu Báo cáo khoa học: Helicobacter pylori acidic stress response factor HP1286 is a YceI

Helicobacter pylori acidic stress response factor HP1286

is a YceI homolog with new binding specificity

Lorenza Sisinni1,2, Laura Cendron1,2, Gabriella Favaro3 and Giuseppe Zanotti1,2

1 Department of Biological Chemistry, University of Padua, Italy

2 Venetian Institute of Molecular Medicine (VIMM), Padua, Italy

3 Department of Chemistry, University of Padua, Italy

Introduction

Helicobacter pylori is a Gram-negative bacterium that

colonizes the human stomach and represents the main

risk factor for peptic ulcers and gastric malignancy

[1,2]. Gastric colonization and persistence of the bacte￾rium in the mucosa significantly rely on proteins

released by it in the surrounding medium [3]. Major

virulence factors that contribute to the inflammatory

response and to epithelial cell damage have been iden￾tified, among them cytotoxin-associated gene protein A

[4,5], vacuolating toxin A [6,7], and H. pylori neutro￾phil-activating protein [8,9]. Other proteins that are

secreted have been identified, but for most of them,

the effective role on secretion and the physiological

effect and relevance of this secretion are often unclear.

One major difficulty in the correct identification of

proteins secreted by H. pylori is its high frequency of

lysis, which results in nonspecific release of the cyto￾plasmic contents of the bacterium [10–12].

Keywords

erucamide; fatty-acid binding proteins;

Helicobacter pylori; lipid binding; lipocalins

Correspondence

G. Zanotti, Department of Biological

Chemistry, University of Padua, Viale

Colombo 3, 35131 Padua, Italy

Fax: +39 049 8073310

Tel: +39 049 8276409

E-mail: [email protected]

Website: http://tiresia.bio.unipd.it/zanotti

Database

The coordinates and structure factors have

been deposited in the Protein Data Bank

(http://www.pdb.org) for immediate release

with ID code 3HPE

(Received 23 December 2009, revised

27 January 2010, accepted 4 February

2010)

doi:10.1111/j.1742-4658.2010.07612.x

HP1286 from Helicobacter pylori is among the proteins that play a relevant

role in bacterial colonization and persistence in the stomach. Indeed, it was

demonstrated to be overexpressed under acidic stress conditions, together

with other essential virulence factors. Here we describe its crystal structure,

determined at 2.1 A˚ resolution. The molecular model, a dimer characterized

by two-fold symmetry, shows that HP1286 structurally belongs to the YceI￾like protein family, which in turn is characterized by the lipocalin fold. The

latter characterizes proteins possessing an internal cavity with the function of

binding and ⁄ or transport of amphiphilic molecules. Surprisingly, a molecule

of erucamide was found bound in the internal cavity of each monomer of

recombinant HP1286, cloned and expressed in an Escherichia coli heterolo￾gous system. The shape and length of the cavity indicate that, at variance

with other members of the family, HP-YceI has a binding specificity for

amphiphilic compounds with a linear chain of about 22 carbon atoms. These

features, along with the fact that the protein is secreted by the bacterium and

is involved in adaptation to an acidic environment, suggest that its function

could be that of sequestering specific fatty acids or amides from the environ￾ment, either to supply the bacterium with the fatty acids necessary for its

metabolism, or to protect and detoxify it from the detergent-like antimicro￾bial activity of fatty acids that are eventually present in the external milieu.

Structured digital abstract

l MINT-7557675: HP 1286 (uniprotkb:O25873) and HP 1286 (uniprotkb:O25873) bind

(MI:0407) by x-ray crystallography (MI:0114)

Abbreviations

RBP, retinol-binding protein; SSI, Structure Screen I; TEV, tobacco etch virus.

1896 FEBS Journal 277 (2010) 1896–1905 ª 2010 The Authors Journal compilation ª 2010 FEBS