AbstractsBiology & Animal Science

More human lives have been lost to tuberculosis than to any other disease and despite the availability of effective short course chemotherapy (DOTS) as well as the Bacilli Calmette Guerin (BCG) vaccine, tuberculosis continues to claim more than a million lives annually. Mycobacterium tuberculosis (M. tuberculosis), the causative agent of tuberculosis, is one of the most successful and scientifically challenging pathogens of all time. However in the last two decades, the ability to perform molecular genetic analysis of M. tuberculosis has resulted in powerful new research tools, while the availability of the complete genome sequence has provided us with a wealth of new information and understanding of the biology of this major pathogen. One of the major challenges, however, is to analyze the properties and functions of those genes that are unique to M. tuberculosis genome. The identification and characterization of such genes which impart various survival strategies employed by M. tuberculosis for successful infection will be of particular significance. One of the important outcomes from the complete genome sequence of M. tuberculosis is the discovery of two multigene families designated PE (99 members) and PPE (69 members) named respectively for the Pro-Glu (PE) and Pro-Pro-Glu (PPE) motifs near the N-terminus of their gene products. In addition to these motifs, proteins of the PE family possess highly homologous N-terminal domains of approximately 100 amino acids (PE domain), whereas the PPE proteins possess a highly homologous N-terminal domain of about 180 amino acids (PPE domain). Although the PE and PPE families of mycobacterial proteins are the focus of intense research, no precise function has so far been unraveled for any member of these families. The current study focuses on Rv3097c gene of M. tuberculosis, a PE family gene that was bioinformatically predicted to be a triacylglycerol hydrolase (lipase). In order to decipher the role of the PE domain, we have carried out functional characterization of the Rv3097c gene (also named lipY) as it was, initially, the only known PE protein for which an enzymatic function (i.e. lipase activity) had been predicted. Further, to understand the function of PE family proteins, an important question that needs to be answered is; whether the PE domain of different PE family proteins has similar or different functions? In this context, our studies were focused on studying the functional role of the PE domain in LipY, as outlined below. In general, the in vivo function and subcellular localization of any protein are integrally connected. PE domain has been reported to be essential for cell wall localization of PE_PGRS33, another PE family protein. Therefore we investigated the subcellular localization of LipY and the influence of the PE domain on subcellular localization of LipY. LipY and a truncated form of LipY lacking the PE domain [LipY(ΔPE)] were expressed in mycobacteria(M. smegmatis and M. bovis BCG). Subcellular fractionation and western blot demonstrated that both…