Clusters of PE and PPE genes of Mycobacterium tuberculosis are organized in operons: Evidence that PE Rv2431c is co‐transcribed with PPE Rv2430c and their gene products interact with each other

Abstract

About 10% of the coding capacity of the Mycobacterium tuberculosis (M. tb) genome is devoted to the PE/PPE family of genes scattered throughout the genome. We have identified 28 PE/PPE operons which are organized within the M. tb genome in such a way that most PE members are upstream to PPE members. One example of such a gene arrangement is the PPE gene Rv2430c, earlier shown by us to code for a highly antigenic protein eliciting strong B-cell responses in TB patients [Choudhary, R.K., Mukhopadhyay, S., Chakhaiyar, P., Sharma, N., Murthy, K.J.R., Katoch V.M. and Hasnain, S.E. (2003) PPE antigen Rv2430c of Mycobacterium tuberculosis induces a strong B cell response. Infect. Immun. 71, 6338-6343], situated downstream to PE gene Rv2431c. Rv2431c and Rv2430c are transcribed as an operon. Expression of either rRv2431c or rRv2430c alone in E. coli limited their localization to the inclusion bodies. However, when they were co-expressed, both the proteins appeared in the soluble fraction. These two proteins interact with each other and form oligomers when alone, however, when present together they exist as heteromer.

P27-PPE36 (Rv2108) Mycobacterium tuberculosis Antigen – Member of PPE Protein Family with Surface Localization and Immunological Activities

“…Genes separated by short intergenic sequences tend to have related function and interact physically (Jacob & Monod, 1961). The structure of a complex of one PE/PPE protein pair was recently characterized (Strong et al, 2006;Tundup et al, 2006). These results indicate that there may be many other instances of interactions between PE and PPE proteins.…”

“…These results indicate that there may be many other instances of interactions between PE and PPE proteins. Like the PE and PPE proteins from the gene Rv2431c (PE25) and Rv2430c (PPE41) that interact together in vitro as probably in vivo (Strong et al, 2006;Tundup et al, 2006), it is stongly probable that PPE36 and PE22 have the same behavior. In fact, computational methods predict that the PE22/PPE36 interaction probability is almost the strongest of all the PE/PPE possible combinations tested (Riley et al, 2008).…”

“…Occasionally, it can be noted that an insertion site IS6110 is localized between this two genes in the strains H37Rv and CDC1551 (Beggs et al, 2000;. Genome analysis by the operon/gene cluster method (Strong et al, 2003;Bowers et al, 2004) suggests that the PE and PPE families are functionally linked (Gey van Pittius et al, 2006;Tekaia et al, 1999;Strong et al, 2006;Tundup et al, 2006). That is, the two genes tend to be in close chromosomal proximity on the Mtb genome (Strong et al, 2003;Bowers et al, 2004).…”

Immunomodulatory Role of Mycobacterial PE/PPE Family of Proteins

“…PE-PGRS and PPE_MPTR genes represent some of the most variable regions of the M.tb chromosome and consequently speculated to represent a major source of antigenic variations which has been reviewed by Sampson (Sampson, 2011). The pe and ppe genes are mostly arranged in a unique regulon with the pe genes located always upstream to the ppe genes and scattered throughout the genome (Tundup et al, 2006). A total of 40 such pe/ppe gene operons exist and 22 of these exclusively contain pe/ ppe gene pairs.…”

An effective system for detecting protein-protein interaction based on in vivo cleavage by PPV NIa protease

“…Meanwhile, some proteins were impaired regarding of biological activity, correct folding, and interacting capability after elaborate steps of manipulation along expression and purification. Another concern is that some interacting proteins only became soluble when all partners were presented together (Kummel et al, 2005;Tundup et al, 2006). New methods based on co-expression strategy offered alternative way to facilitate the process of protein expression and protein-protein interaction, by using compatible vectors (Huppa and Ploegh, 1997;Fabian et al, 1998;Hanzlowsky et al, 2006), multiple promoters (Belyaev and Roy, 1993;Scheich et al, 2007), polycistrons (Selleck et al, 2005;Neumann et al, 2007;Bieniossek et al, 2009), fusion linkers (Clements et al, 2000) in both prokaryotic and eukaryotic systems.…”