Tài liệu Báo cáo khoa học: The structure of the carbohydrate backbone of the lipopolysaccharide from

The structure of the carbohydrate backbone of the lipopolysaccharide

from Acinetobacter baumannii strain ATCC 19606

Evgeny V. Vinogradov1,

*, Jens é. Duus1

, Helmut Brade2 and Otto Holst2

1

Department of Chemistry, Carlsberg Laboratory, Valby, Copenhagen, Denmark; 2

Division of Medical and Biochemical Microbiology,

Research Center Borstel, Borstel, Germany

The chemical structure of the phosphorylated carbohydrate

backbone of the lipopolysaccharide (LPS) from Acineto￾bacter baumannii strain ATCC 19606 was investigated by

chemical analysis and NMR spectroscopy of oligosaccha￾rides obtained after deacylation or mild acid hydrolysis.

From the combined information the following carbohydrate

backbones can be deduced:

a-GalpNR1

b-GlcpN a-Kdo

1 1 2

¯ ¯ ¯

4 7 4

R2

®3)-a-GlcpNAcA-(1®4)-a-Kdo-(2®5)-a-Kdo-(2®6)-b-GlcpN4P-(1®6)-a-GlcpN1P

where R1ˆ H and R2 ˆ a-Glcp-(1 ® 2)-b-Glcp-(1 ® 4)-b￾Glcp-(1 ® 4)-b-Glcp-(1 as major and R1 ˆ Ac and R2 ˆ H

as minor products.

All monosaccharides are D-con®gured. Also, smaller oli￾gosaccharide phosphates were identi®ed that are thought to

represent degradation products of the above structures.

Keywords: Acinetobacter baumannii; lipopolysaccharide;

core region; structural analysis; NMR spectroscopy.

The Gram-negative bacterium Acinetobacter (Moraxella￾ceae) is isolated from soil and water which represent its

natural habitats. However, the genus has gained increasing

importance as a causative agent of nosocomial infections

(e.g. bacteremia, secondary meningitis) in recent years [1].

As in other Gram-negative bacteria, Acinetobacter pos￾sesses lipopolysaccharides (LPS) in the outer membrane of

the cell wall that have been shown to represent useful

chemotaxonomic and antigenic markers for its identi®ca￾tion and differentiation. The occurrence of S-form LPS in

Acinetobacter has unequivocally been proven recently, and

the structures of a number of O-speci®c polysaccharides

and their antigenic characterization have been published

[2±9]. The core region of Acinetobacter LPS possesses

particular structural features which clearly distinguish it

from other core structures [10]. First, it belongs to the

group of heptose-de®cient core regions. Second, it may

contain D-glycero-D-talo-oct-2-ulopyranosonic acid (Ko)

which can replace the 3-deoxy-D-manno-oct-2-ulopyrano￾sonic acid (Kdo) residue linking the core region to lipid A

[11±15].

Another core type has been identi®ed in A. baumannii

strain NCTC 10303 [16] that is devoid of Ko. It comprises

the tetrasaccharide a-Kdo-(2 ® 5)-[a-Kdo-(2 ® 4)-]-a￾Kdo-(2 ® 5)-a-Kdo-(2 ® [a-Kdo IV-(a-Kdo III)-a-Kdo

II-a-Kdo I], of which Kdo IV is substituted at O-8 by a

short-chain rhamnan and Kdo III at O-4 by the disaccha￾ride a-D-GlcpNAc-(1 ® 4)-a-D-GlcpNA (GlcpNA, 2-ami￾no-2-deoxy-glucopyranosuronic acid). Kdo I links the core

region to the lipid A. This Kdo tetrasaccharide is unique in

nature; however, a second Kdo tetrasaccharide of different

structure has been identi®ed in LPS of Chlamydophila

psittaci 6BC [17]. The latter has been shown to be assembled

by one Kdo transferase, which is therefore multifunctional

[18]. However, the biosynthesis of the Kdo-tetrasaccharide

from LPS of A. baumannii strain NCTC 10303 has not yet

been elucidated. For A. baumannii strain ATCC 15303,

which possesses in its LPS core region the trisaccharide

a-Kdo-(2 ® 5)-[a-Kdo-(2 ® 4)-]-a-Kdo-(2 ® , it has been

shown that the Kdo transferase is able to transfer the ®rst

two a-(2 ® 4)-linked Kdo residues [19]. The mechanism of

the transfer of the third Kdo residue has not yet been

identi®ed.

In addition to the work on the determination of the

chemical and antigenic structures of O-speci®c polysaccha￾rides from LPS of Acinetobacter in order to establish an

O-serotyping scheme, there exists considerable interest in

investigating the LPS core regions from this genus which

obviously allows novel insights in structure, genetics and

biosynthesis of LPS. Here, the structures of the carbohy￾drate backbones of the LPS from A. baumannii strain

ATCC 19606 are reported.

Correspondence to O. Holst, Research Center Borstel, Parkallee 22,

D-23845 Borstel, Germany. Fax: + 49 4537 188419,

Tel.: + 49 4537 188472, E-mail: [email protected]

Abbreviations: LPS, lipopolysaccharide; GlcpNAcA, 2-acetamido-2-

deoxy-glucopyranosyluronic acid; DGlcpNA, 2-amino-2,4-dideoxy-b￾L-threo-hex-4-enopyranosyluronic acid; HMBC, heteronuclear mul￾tiple bond correlation; HMQC, heteronuclear multiple quantum co￾herence; HPAEC, high-performance anion-exchange

chromatography; Kdo, 3-deoxy-D-manno-oct-2-ulopyranosonic acid.

Dedication: this article is dedicated to Prof Dr Joachim Thiem,

Institute of Organic Chemistry, University of Hamburg, Germany on

the occasion of his 60th birthday.

*Present address: Institute for Biological Sciences, National Research

Council Canada, Ottawa, Ontario K1A 0R6, Canada.

(Received 23 July 2001, revised 29 October 2001, accepted 31 October

2001)

Eur. J. Biochem. 269, 422±430 (2002) Ó FEBS 2002