Transcriptional Studies on a Deletion Mutant: -Acetylglycyl-Clavaminic Acid Is an Intermediate of Clavulanic Acid Biosynthesis.

The gene encodes an oligopeptide-binding protein similar to the periplasmic substrate-binding proteins of the ABC transport systems. However, is an orphan gene, not included in an ABC operon. This gene is located in the clavulanic acid (CA) gene cluster of and is essential for CA production. A transcriptomic study of the -null mutant Δ:: showed changes in the expression levels of 233 genes from those in the parental strain. These include genes for ABC transport systems, secreted proteins, peptidases, and proteases. Expression of the clavulanic acid, clavam, and cephamycin C biosynthesis gene clusters was not significantly affected in the deletion mutant. The genes for holomycin biosynthesis were upregulated 2-fold on average, and the level of upregulation increased to 43-fold in a double mutant lacking and the pSCL4 plasmid. Strains in which was mutated secreted into the culture the compound -acetylglycyl-clavaminic acid (AGCA), a putative intermediate of CA biosynthesis. A culture broth containing AGCA, or AGCA purified by liquid chromatography-mass spectrometry (LC-MS), was added to the cultures of various non-CA-producing mutants. Mutants blocked in the early steps of the pathway restored CA production, whereas mutants altered in late steps did not, establishing that AGCA is a late intermediate of the biosynthetic pathway, which is released from the cells when the oligopeptide-binding protein OppA2 is not available. The gene encodes an oligopeptide permease essential for the production of clavulanic acid. A transcriptomic analysis of Δ:: in comparison to the parental strain ATCC 27064 is reported. The lack of OppA2 results in different expression of 233 genes, including genes for proteases and genes for transport systems. The expression of the clavulanic acid genes in the mutant is not significantly affected, but the genes for holomycin biosynthesis are strongly upregulated, in agreement with the higher holomycin production by this strain. The -mutant is known to release -acetylglycyl-clavaminic acid to the broth. Cosynthesis assays using non-clavulanic acid-producing mutants showed that the addition of pure -acetylglycyl-clavaminic acid to mutants in which clavulanic acid formation was blocked resulted in the recovery of clavulanic acid production, but only in mutants blocked in the early steps of the pathway. This suggests that -acetylglycyl-clavaminic acid is a previously unknown late intermediate of the clavulanic acid pathway.