Involvement of colicin in the limited protection of the colicin producing cells
against bacteriophage
Yu-Hui Lina,
1, Chen-Chung Liaoa,
1, Po-Huang Liangb,
Hanna S. Yuanc
and Kin-Fu Chak
a Institute of Biochemistry,
University System of Taiwan–National Yang Ming University, Shih-Pai, Taipei
11221, Taiwan, ROC
b Institute of Biological Chemistry, Academia Sinica, Taipei 11529,
Taiwan, ROC
c Institute of Molecular Biology, Academia Sinica, Taipei 11529,
Taiwan, ROC
Received 19 March 2004. Available online 13 April 2004.
Abstract
The restriction/modification
system is considered to be the most common machinery of microorganisms for
protection against bacteriophage infection. However, we found that mitomycin C
induced Escherichia coli containing ColE7-K317 can confer limited
protection against bacteriophage M13K07 and
infection. Our study showed that degree of protection is correlated with the
expression level of the ColE7 operon, indicating that colicin E7 alone or the
colicin E7-immunity protein complex is directly involved in this protection
mechanism. It was also noted that the degree of protection is greater against
the single-strand DNA bacteriophage M13K07 than the double-strand
bacteriophage .
Coincidently, the KA value of ColE7-Im either interacting
with single-strand DNA (2.94 × 105 M−1) or double-strand
DNA (1.75 × 105 M−1) reveals that the binding affinity
of ColE7-Im with ssDNA is 1.68-fold stronger than that of the protein complex
interacting with dsDNA. Interaction between colicin and the DNA may play a
central role in this limited protection of the colicin-producing cell against
bacteriophages. Based on these observations, we suggest that the colicin
exporting pathway may interact to some extent with the bacteriophage infection
pathway leading to a limited selective advantage for and limited protection of
colicin-producing cells against different bacteriophages.
|