Role of maturation of lysis protein in the processes of colicin release

• Main Authors: Lung-JR Lin, 林隆誌
• Other Authors: Kin-Fu Chak
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/24407005044867585985

博士 === 國立陽明大學 === 生化暨分子生物研究所 === 97 === Colicin E7 was one of nuclease type colicins secreting by Escherichia coli. It was encoded on pColE7-K317 plasmid that there were also encoded the inhibitor of colicin E7 (immunity protein) and a small lipoprotein (lysis protein). The mechanism of secretion of colicin E7 was still unclear. The small lipoprotein, the lysis protein, played the most important role in secretion of colicin E7. The mature lysis protein was translocated to the inner leaf of outer membrane and activated outer membrane phospholipase A to cause the quasis-lysis. We detected the ratio of extracellular and intracellular colicins by ELISA. It was found that the secretion of colicin was earlier than the decline in culture turbidity. The TO/PI staining showed that the permeability of inner membrane was increased in short time after induction to expression of lysis proteins. Point mutated lysis proteins was found that lipomodification of lysis protein made the inner membrane permeable. Increasing of the permeability of outer membrane was later than inner membrane detected by the NPN assay. The phospholipase A defective strain was found that the mature lysis protein increased the permeability of outer membrane independently. We also pointed that the secretion of colicin was happened in the OMPLA defective strain. The TO/PI staining and NPN assay showed that the maturation of lysis proteins increased permeability of membranes same with the wild-type strain. We found lower permeability of outer membrane in the OMPLA defective stain than the wide-type strain after long term induction. It indicated that OMPLA was major factor to make the quasislysis. The immuno-EM data showed that the lysis protein located on the inner leaf of outer membrane and polymerizated to make cell envelop fusion. Our observed that colicin E7 was secreted through fusion sites. The lysis protein disturbed host cell membrane and make colicin E7 secret to the environment.