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Xin Sun,Ruyan Li,Guochen Wan,Wanli Peng,Shuangjun Lin,Zixin Deng,Rubing Liang 한국미생물학회 2021 The journal of microbiology Vol.59 No.2
Putrescine, a typical polyamine compound important for cell growth and stress resistance, can be utilized as an energy source. However, the regulation of its catabolism is unclear. Here the small RNA (sRNA) Spot 42, an essential regulator of carbon catabolite repression (CCR), was confirmed to participate in the post-transcriptional regulation of putrescine catabolism in Escherichia coli. Its encoding gene spf exclusively exists in the γ-proteobacteria and contains specific binding sites to the 5 -untranslated regions of the puuE gene, which encodes transaminase in the glutamylated putrescine pathway of putrescine catabolism converting γ-aminobutyrate (GABA) into succinate semialdehyde (SSA). The transcription of the spf gene was induced by glucose, inhibited by putrescine, and unaffected by PuuR, the repressor of puu genes. Excess Spot 42 repressed the expression of PuuE significantly in an antisense mechanism through the direct and specific base-pairing between the 51–57 nt of Spot 42 and the 5 - UTR of puuE. Interestingly, Spot 42 mainly influenced the stability of the puuCBE transcript. This work revealed the regulatory role of Spot 42 in putrescine catabolism, in the switch between favorable and non-favorable carbon source utilization, and in the balance of metabolism of carbon and nitrogen sources.
Lee, Mi-Jin,Kong, Dekun,Han, Kyuboem,Sherman, David H,Bai, Linquan,Deng, Zixin,Lin, Shuangjun,Kim, Eung-Soo Springer International 2012 Applied microbiology and biotechnology Vol.95 No.1
<P>Polyene antibiotics such as nystatin are a large family of very valuable antifungal polyketide compounds typically produced by soil actinomycetes. Previously, using a polyene cytochrome P450 hydroxylase-specific genome screening strategy, Pseudonocardia autotrophica KCTC9441 was determined to contain an approximately 125.7-kb region of contiguous DNA with a total of 23 open reading frames, which are involved in the biosynthesis and regulation of a structurally unique polyene natural product named NPP. Here, we report the complete structure of NPP, which contains an aglycone identical to nystatin and harbors a unique di-sugar moiety, mycosaminyl-(α1-4)-N-acetyl-glucosamine. A mutant generated by inactivation of a sole glycosyltransferase gene (nppDI) within the npp gene cluster can be complemented in trans either by nppDI-encoded protein or by its nystatin counterpart, NysDI, suggesting that the two sugars might be attached by two different glycosyltransferases. Compared with nystatin (which bears a single sugar moiety), the di-sugar containing NPP exhibits approximately 300-fold higher water solubility and 10-fold reduced hemolytic activity, while retaining about 50% antifungal activity against Candida albicans. These characteristics reveal NPP as a promising candidate for further development into a pharmacokinetically improved, less-cytotoxic polyene antifungal antibiotic.</P>