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Escherichia coli Signal Peptidase Recognizes and Cleaves the Signal Sequence of Xylanase from a Newly Isolated Bacillus subtilis Strain R5

A. Jalal1, N. Rashid1*, N. Ahmed1, S. Iftikhar1, and M. Akhtar1,2

1School of Biological Sciences, University of the Punjab, Lahore 54590, Pakistan; fax: +92-42-9923-0980; E-mail: naeem.ff@sbs.pu.edu.pk; naeemrashid37@hotmail.com

2School of Biological Sciences, University of Southampton, Southampton SO16 7PX, England

* To whom correspondence should be addressed.

Received September 6, 2010; Revision received September 24, 2010
A gene encoding the xylanase from Bacillus subtilis strain R5 containing the native signal sequence was cloned and expressed in Escherichia coli. The heterologous expression of the gene resulted in the production of the recombinant protein in the cytoplasm as well as its secretion into the culture medium. The xylanase activity in the culture medium increased with time after induction up to 90% of the total activity in 14 h. Molecular mass and N-terminal amino acid sequence determinations of the purified recombinant xylanase revealed that the native signal peptide was cleaved off by E. coli signal peptidases between Ala28 and Ala29.
KEY WORDS: xylanase, Bacillus subtilis strain R5, signal peptide, purification, MALDI-TOF mass spectrometry

DOI: 10.1134/S0006297911030084