Title |
In silico analysis and experimental validation of lipoprotein and novel Tat signal peptides processing in Anabaena sp. PCC7120 |
Author |
Sonika Kumari and Akhilesh Kumar Chaurasia* |
Address |
Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085, India |
Bibliography |
Journal of Microbiology, 53(12),837-846, 2015,
|
DOI |
10.1007/s12275-015-5281-3
|
Key Words |
Anabaena sp. PCC7120, lipoprotein signal peptide,
bipartite signal peptide, protein transport, twin arginines
translocase, Sec pathway |
Abstract |
Signal peptide (SP) plays a pivotal role in protein translocation.
Lipoprotein- and twin arginine translocase (Tat) dependent
signal peptides were studied in All3087, a homolog of
competence protein of Synechocystis PCC6803 and in two
putative alkaline phosphatases (ALPs, Alr2234 and Alr4976),
respectively. In silico analysis of All3087 is shown to possess
the characteristics feature of competence proteins such as
helix-hairpin-helix, N and C-terminal HKD endonuclease
domain, calcium binding domain and N-terminal lipoprotein
signal peptide. The SP recognition-cleavage site in All3087
was predicted (AIA-AC) using SignalP while further in-depth
analysis using Pred-Lipo and WebLogo analysis for consensus
sequence showed it as IAA-C. Activities of putative
ALPs were confirmed by heterologous overexpression, activity
assessment and zymogram analysis. ALP activity in
Anabaena remains cell bound in log-phase, but during late
log/stationary phase, an enhanced ALP activity was detected
in extracellular milieu. The enhancement of ALP activity
during stationary phase was not only due to inorganic phosphate
limitation but also contributed by the presence of novel
bipartite Tat-SP. The Tat signal transported the folded active
ALPs to the membrane, followed by anchoring into the
membrane and successive cleavage enabling transportation
of the ALPs to the extracellular milieu, because of bipartite
architecture and processing of transit Tat-SP. |