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Infection and Immunity, February 2001, p. 640-649, Vol. 69, No. 2
Department of Enteric Infections, Walter Reed
Army Institute of Research, Silver Spring, Maryland
20910-7500,1 and Gastrointestinal
Research Laboratory, Veterans Administration Medical Center, San
Francisco, California 941212
Received 16 March 2000/Returned for modification 8 May
2000/Accepted 26 October 2000
Escherichia coli strain RDEC-1 causes a diarrheagenic
infection in rabbits with AF/R1 fimbriae, which have been identified as
an important colonization factor in RDEC-1 adherence leading to
disease. The AF/R1-mediated RDEC-1 adherence model has been used as a
model systems for E. coli diarrheal diseases. In this study, RDEC-1 adhered specifically to small intestinal brush borders, with both sialic acid and
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.2.640-649.2001
Escherichia coli Strain RDEC-1 AF/R1
Endogenous Fimbrial Glycoconjugate Receptor Molecules in Rabbit
Small Intestine

-galactosyl residues apparently involved. The AF/R1-mediated adherence activity of [14C]-labeled
RDEC-1 was analyzed quantitatively by using 24-well plates coated with
purified brush borders and purified microvilli. Two microvillus
membrane proteins (130 and 140 kDa) were individually isolated, and
chicken antibody raised to each protein inhibited bacterial adherence.
These same two proteins, previously shown to be recognized by AF/R1,
were individually digested with trypsin, and the amino acid sequences
of peptides were determined by reversed-phase capillary liquid
chromatography-mass spectrometry tandem mass spectrometry (LC-MS). This
LC-MS analysis indicated that these proteins are subunits of the rabbit
sucrase-isomaltase protein (SI) complex. Guinea pig serum raised to
purified rabbit SI complex inhibited bacterial adherence to microvilli.
Additionally, as determined by high-performance thin-layer
chromatography and autoradiography, RDEC-1 adhered selectively, via
AF/R1 fimbriae, to a glycolipid tentatively identified as
galactosylceramide (Gal
1-1Cer) in the lipid extract of rabbit small
intestinal brush borders. RDEC-1 adherence to Gal
1-1Cer was
partially inhibited in the presence of galactose. These combined
results indicate that the endogenous receptor molecule for AF/R1
fimbriae of RDEC-1 is each individual component of the SI complex,
although binding to glycolipid may be responsible for an additional
adherence mechanism.
*
Corresponding author. Mailing address: Department of
Enteric Infections, Walter Reed Army Institute of Research, 503 Robert Grant Ave., Silver Spring, MD 20910-7500. Phone: (301) 319-9798. Fax:
(301) 319-9801. E-mail:
fred.cassels{at}na.amedd.army.mil.
Present address: Department of Biochemistry, Yeungnam University,
Kyungsan, 712-749 Republic of Korea.
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