©1996-2019. All Rights Reserved. Online Journal of Bioinformatics . You may not store these pages in any form except for your own personal use. All other usage or distribution is illegal under international copyright treaties. Permission to use any of these pages in any other way besides the before mentioned must be gained in writing from the publisher. This article is exclusively copyrighted in its entirety to OJB publications. This article may be copied once but may not be, reproduced or re-transmitted without the express permission of the editors. This journal satisfies the refereeing requirements (DEST) for the Higher Education Research Data Collection (Australia). Linking:To link to this page or any pages linking to this page you must link directly to this page only here rather than put up your own page.
OJBTM
Online Journal of Bioinformatics ©
Volume 10 (2): 241-258, 2009.
Effect
of iron deprivation on expression of sphingomyelase
in pathogenic serovar Lai.
Sridhar Velineni1, Sanam Ramadevi2, Swapna
Asuthkar1, Manjula Sritharan1*
1Department of Animal Sciences,
University of Hyderabad, Hyderabad, India; 2Informatics Division,
GVK Biosciences Pvt Ltd, Hyderabad, India.
Velineni S, Ramadevi
S, Asuthkar S, Sritharan
M., Effect of iron deprivation on expression of sphingomyelase
in pathogenic serovar Lai, Onl
J Bioinform, 10 (2): 241-258, 2009. Hemolysins are one of the contributing
virulence factors in pathogenic Leptospira spp.
The genome of Leptospira interrogans serovar Lai
contains ten hemolysin genes, encoding molecules with
sphingomyelinase and phospholipase activities. The sphingomyelinase genes are
absent in the non-pathogenic Leptospira biflexa serovar Patoc that, however harbors the genes for the hemolysins with phospholipase activity. In general,
bacterial hemolysins are secreted into the immediate
environment of the host and lyse the host cells with the release of the
intracellular nutrients, including iron. Iron limitation in bacteria
induces not only the iron acquisition machinery but also the expression of
bacterial virulence determinants and toxins. Our earlier observations on the
iron-regulated hemin-binding protein HbpA in serovar Lai was the first report on the direct acquisition
of iron by this pathogen. In the present study, the iron-regulated expression
of sphingomyelinase in outer membrane vesicles (OMVs) is demonstrated. The OMVs
from low iron cultures showed not only sphingomyelinase but also the
iron-regulated hemin-binding protein HbpA, both of
which were absent in the corresponding high iron samples. LipL32
(hemolysis-associated protein, hap-1) was present in both high and low iron
OMVs. None of the above three proteins were expressed by the non-pathogenic L.
biflexa serovar Andamana. The release of the OMVs from the surface of the
pathogen was demonstrated by transmission electron microscopy.
Immunofluorescence studies using confocal microscopy showed the surface
association of sphingomyelinase in low iron organisms. We also identified a 63 kDa outer membrane protein by immunoprecipitation with
anti-sphingomyelinase antibodies. The protein was identified as the outer
membrane efflux protein TolC (LA0957, Swiss Prot Q8F718) by sequence analysis using tandem mass
spectrometry. The possible role of this protein in the transport of
sphingomyelinase is discussed based on the similarity of protein folding to TolC of E. coli and the detection of hlyB and hlyD in
the genome of serovar Lai.
Key words: Iron, hemolysin,
Leptospira, sphingomyelinase, outer membrane
efflux protein, TolC.
FULL-TEXT(SUBSCRIPTION OR
PURCHASE TITLE $25USD)