Proteomic profiling of L-cysteine induced selenite resistance in Enterobacter sp. YSU

doi:10.1186/1477-5956-7-30

Proteome Science

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Jasenec A
Barasa N
Kulkarni S
Shaik N
Moparthi S
Konda V
Caguiat J

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Barasa N
Kulkarni S
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Konda V
Caguiat J
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Proteomic profiling of L-cysteine induced selenite resistance in Enterobacter sp. YSU

Ashley Jasenec , Nathaniel Barasa , Samatha Kulkarni , Nabeel Shaik , Swarnalatha Moparthi , Venkataramana Konda and Jonathan Caguiat

Department of Biological Sciences, Proteomics/Genomics Research Group, Youngstown State University, One University Plaza, Youngstown, OH 44555, USA

author email corresponding author email

Proteome Science 2009, 7:30doi:10.1186/1477-5956-7-30


Published:	28 August 2009

Abstract

Background

Enterobacter sp. YSU is resistant to several different heavy metal salts, including selenite. A previous study using M-9 minimal medium showed that when the selenite concentration was 100,000 times higher than the sulfate concentration, selenite entered Escherichia coli cells using two pathways: a specific and a non-specific pathway. In the specific pathway, selenite entered the cells through a yet to be characterized channel dedicated for selenite. In the non-specific pathway, selenite entered the cells through a sulfate permease channel. Addition of L-cystine, an L-cysteine dimer, appeared to indirectly decrease selenite import into the cell through the non-specific pathway. However, it did not affect the level of selenite transport into the cell through the specific pathway.

Results

Growth curves using M-9 minimal medium containing 40 mM selenite and 1 mM sulfate showed that Enterobacter sp. YSU grew when L-cysteine was present but died when it was absent. Differential protein expression analysis by two dimensional gel electrophoresis showed that CysK was present in cultures containing selenite and lacking L-cysteine but absent in cultures containing both selenite and L-cysteine. Additional RT-PCR studies demonstrated that transcripts for the sulfate permease genes, cysA, cysT and cysW, were down-regulated in the presence of L-cysteine.

Conclusion

L-cysteine appeared to confer selenite resistance upon Enterobacter sp. YSU by decreasing the level of selenite transport into the cell through the non-specific pathway.