Global Regulator of Rubber Degradation in Gordonia polyisoprenivorans VH2: Identification and Involvement in the Regulation Network.

A cAMP receptor protein (CRPVH2) was detected as a global regulator in Gordonia polyisoprenivorans VH2 and was proposed to participate in the network regulating poly(cis-1,4-isoprene) degradation as a novel key regulator. CRPVH2 shares a sequence identity of 79% with GlxR, a well-studied global regulator of Corynebacterium glutamicum. Furthermore, CRPVH2 and GlxR have a common oligomerization state and similar binding motifs, and thus most likely have similar functions as global regulators. Size exclusion chromatography of purified CRPVH2 confirmed the existence as a homodimer with a native molecular weight of 44.1 kDa in the presence of cAMP. CRPVH2 bound to the TGTGAN6TCACT motif within the 131-bp intergenic region of divergently oriented lcp1VH2 and lcpRVH2, encoding a latex clearing protein and its putative repressor, respectively. DNase I footprinting assays revealed the exact operator size of CRPVH2 in the intergenic region (25 bp), which partly overlapped with the proposed promoters of lcpRVH2 and lcp1VH2. Our findings indicate that CRPVH2 represses the expression of lcpRVH2 while simultaneously directly or indirectly activating the expression of lcp1VH2 by binding the competing promoter regions. Furthermore, binding of CRPVH2 to upstream regions of additional putative enzymes of poly(cis-1,4-isoprene) degradation was verified in vitro. In silico analyses predicted 206 CRPVH2 binding sites comprising 244 genes associated with several functional categories, including carbon and peptide metabolism, stress response, etc. The gene expression regulation of several subordinated regulators substantiated the function of CRPVH2 as a global regulator. Moreover, we anticipate that the novel lcpR regulation mechanism by CRPs is widespread in other rubber-degrading actinomycetes. [ABSTRACT FROM AUTHOR]