Farhan Younas

• Caulobacter crescentus is well-known for its unique dimorphic life style. It is used as a model organism to study cell division and differentiation. A range of interesting features constitute its unique nature. It is normally found in dilute organic environments and was believed to be lacking any genes coding for porin like proteins. We found channel forming activity in the enriched cell wall extracts of the organism. The protein responsible for the porin like activity was found to be a member of the OmpW family. The protein formed small cation selective channels in artificial lipid bilayers. In order to confirm that the studied protein is responsible for the channel forming activity, an ompW knockout strain of C. crescentus was developed. Enriched outer membrane extracts from the mutant strain did not show channel forming activity. We also identified and characterized a homologue of hVDAC-1 in Legionella pneumophila. L. pneumophila has genes coding for a range of eukaryotic like protein. We were especially interested in the gene lpg1974 which codes for Lpg1974, a protein which had reasonable similarity to hVDAC-1. The protein was found to produce large anion selective channels in artificial lipid bilayers. We also developed a homology structure for the protein which had remarkable similarity to hVDAC-1. Here we further studied the properties of the protein, by expressing the protein without its predicted N-terminal signal peptide (Lpg1974Δ1-21). There are a series of diverse reports about the importance of the N-terminal sequence. The truncated protein formed large anion selective channels. The voltage sensitivity of the protein was not affected by the signal peptide deletion.