Hindawi Publishing Corporation International Journal of Microbiology Volume 2010, Article ID 196363, 7 pages doi:10.1155/2010/196363 Research Article Characterization of the Escherichia coli Antifungal Protein PPEBL21 V. Yadav, 1 R. Mandhan, 2 M. Kumar, 3 J. Gupta, 4 and G. L. Sharma 3 1 National Institute for Health, Rockville Pike, Bethesda, MD 20892, USA 2 Department of Biotechnology, Kurukshetra University, Kurukshetra 136119, India 3 Institute of Genomics and Integrative Biology, Mall Road, Delhi 110007, India 4 Research Institute of the McGill University Health Centre, Montr´ eal, QC, Canada H3G 1A4 Correspondence should be addressed to G. L. Sharma, drglsharma@hotmail.com Received 22 December 2009; Accepted 9 March 2010 Academic Editor: Marco Gobbetti Copyright © 2010 V. Yadav et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. An antifungal protein isolated from Escherichia coli BL21 (PPEBL21) and predicted to be alcohol dehydrogenase (ADH) was subjected to biological characterization. The PPEBL21, indeed, demonstrated propionaldehyde-specific ADH activity. The Km and Vmax of PPEBL21 were found to be 644.8 μM and 1.2U/mg, respectively. In-gel activity assay also showed that PPEBL21 was a propionaldehyde-specific ADH. The pI of PPEBL21 was observed to be 7.8. PPEBL21 was found to be stable up to a temperature of 40 ◦ C with optimum activity at pH 7.5. The decrease in pH decreased the activity of PPEBL21. These results suggested that PPEBL21 having alcohol dehydrogenase activity and stability at significantly high temperature might be an important lead antifungal molecule. Experiments were performed to identify the possible target of PPEBL21 in the pathogen A. fumigatus. Results revealed that PPEBL21 inhibited completely the expression of a 16 kDa protein in A. fumigatus. The 16 kDa protein of A. fumigatus targeted by PPEBL21 was identified as a hypothetical protein by peptide mass fingerprinting. It is thus hypothesized that a 16 kDa factor is essentially required by A. fumigatus for survival and its impaired synthesis due to treatment with PPEBL21 may lead to the death of pathogen. 1. Introduction The need for developing new, safe and more effective antifungal drugs has been a major challenge today, especially with alarming increase in the incidence of opportunistic life-threatening fungal infections due to variety of factors including indiscriminate use of antibiotics, immunosuppres- sive therapies, blood transfusions, organ transplantation, and underlying diseases such as aplastic anemia, AIDS, chronic granulomatous disease, and Job’s syndrome [1]. The history of new drug discovery processes has shown that novel skeletons with antimycotic properties have, in the majority of cases, come from natural sources [2]. There have been efforts which involved the screening of plants and microorganisms for antimycotic properties [3–5]. However, the progress on the search for new, broad-spectrum antifungal compounds with greater potency has been very slow [6]. One reason for the slow progress compared to antibacterials has been that, like mammalian cells, fungi are also eukaryotes and therefore agents that inhibit protein, RNA, or DNA biosynthesis in fungi have a greater potential for toxicity to the host as well [7]. Another reason has been that, until recently, the incidence of life threatening fungal infections was perceived as being too low to warrant aggressive research aiming at developing ideal antifungal formulations [8]. Under a research programme on new drug development, we evaluated a panel of bacteria for antimycotic potential [9]. It was observed that Escherichia coli strain BL21 possessed antifungal properties and its activity was associated with a 39.30 kDa protein synthesized by E. coli BL21 [10]. The primary amino acid structure of 39.30 kDa protein of E. coli BL21 (PPEBL21) did not resemble that of antifungal proteins described so far and therefore, it could be an important lead from different class of molecules. The present study was undertaken to characterize the PPEBL21 partially. Attempts were also made to identify the target(s) of PPEBL21 in A. fumigatus that might play a role in the survival of the pathogen.