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Proteomic Analysis of the Secretome of Haloarchaeon Natrinema sp. J7–2
journal contribution
posted on 2014-03-07, 00:00 authored by Jie Feng, Jian Wang, Yaoxin Zhang, Xin Du, Zhisheng Xu, Yufeng Wu, Wei Tang, Moran Li, Bing Tang, Xiao-Feng TangAlthough in silico predictions have revealed that
haloarchaea can be distinguished from other organisms in that the
Tat pathway is used more extensively than the Sec pathway for haloarchaeal
protein secretion, only a few haloarchaeal-secreted proteins have
been experimentally confirmed. Here, the culture supernatant and membrane
fraction of the haloarchaeon Natrinema sp. J7–2
grown at 23% salt concentration were subjected to RPLC–ESI–MS/MS
analysis. In total, 46 predicted Tat substrates, 14 predicted Sec
substrates, and 3 class III signal peptide-bearing proteins were detected.
Approximately 65% of the detected Tat substrates contain lipoboxes,
emphasizing the role of the Tat pathway in haloarchaeal lipoprotein
secretion. Most of the detected Tat substrates are extracellular substrate
(solute)-binding proteins and redox proteins. Despite the small number
of Sec substrates, two of them, a cell surface glycoprotein and a
putative lipoprotein carrier protein, were identified to be high-abundance
secreted proteins. While limited proteins were detected in the culture
supernatant, most of the secreted proteins were found in the membrane
fraction. The anchoring of secreted proteins to the cell surface via
a lipobox or a PGF-CTERM seems to be an adaptation strategy of haloarchaea
to handle the harsh extracellular environment. Additionally, ∼15%
of the integral membrane proteins (IMPs) detected in the membrane
fraction possess putative Sec signal peptides or signal anchors, implying
that the Sec pathway is important for membrane insertion of IMPs.
This is the first report to describe the experimental secretome of
haloarchaea and provide new information for better understanding of
haloarchaeal protein secretion patterns.
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Keywords
integral membrane proteinsHaloarchaeon Natrinema spSec signal peptidesmembrane fractionhaloarchaeal protein secretion patternsRPLCSec substrateshaloarchaeal lipoprotein secretionhaloarchaeal protein secretionTat pathwaySec pathwaycell surface glycoproteinlipoprotein carrier proteinhaloarchaeon Natrinema spIMPIIITat substrates
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