LAUSR

A cAMP receptor protein (CRPVH2) was detected as global regulator in Gordonia polyisoprenivorans VH2 and was supposed to participate in the network regulating poly(cis-1,4-isoprene) degradation as 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, similar binding motifs and thus most likely 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. It bound to the TGTGAN6TCACT motif within the 131 bp intergenic region of divergently oriented lcp1 VH2 and lcpR VH2, 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), that partly overlapped with the proposed promoters of lcpR VH2 and lcp1 VH2 Our findings indicate that CRPVH2 represses the expression of lcpR VH2 while simultaneously (in-) directly activating the expression of lcp1 VH2 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 global regulator. Moreover, we anticipate that the novel lcpR regulation mechanism by CRPs is widespread in other rubber-degrading actinomycetes.Importance In order to develop efficient microbial recycling strategies for rubber waste materials, it is inevitable to enlighten the degradation pathway of the polymer and its regulation. However, only little is known about the transcriptional regulation of the rubber degradation pathway, that seems to be upregulated in the presence of the polymer. We identified a novel key regulator of rubber degradation (CRPVH2) that regulates several parts of the pathway in the potent rubber-degrader G. polyisoprenivorans VH2. Furthermore, we provide evidence for a widespread involvement of CRP regulators in the degradation of rubber in various other rubber-degrading actinomycetes. Thus, the novel insights into the regulation of rubber degradation are essential for developing efficient microbial degradation strategies of the rubber waste materials by the group of actinomycetes.