2-Alkyl-4-hydroxymethylfuran-3-carboxylic acids, antibiotic production inducers discovered by Streptomyces coelicolor genome mining

Abstract

All of the genetic elements necessary for the production of the antibiotic methylenomycin (Mm) and its regulation are contained within the 22-kb mmy-mmf gene cluster, which is located on the 356-kb linear plasmid SCP1 of Streptomyces coelicolor A3(2). A putative operon of 3 genes within this gene cluster, mmfLHP, was proposed to direct the biosynthesis of an A-factor-like signaling molecule, which could play a role in the regulation of Mm biosynthesis. The mmfLHP operon was expressed under the control of its native promoter in S. coelicolor M512, a host lacking the SCP1 plasmid, and the ability to produce prodiginine and actinorhodin antibiotics. Comparative metabolic profiling led to the identification and structure elucidation of a family of 5 new 2-alkyl-4-hydroxymethylfuran-3-carboxylic acids (AHFCAs), collectively termed Mm furans (MMFs), as the products of the mmfLHP genes. MMFs specifically induce the production of the Mm antibiotics in S. coelicolor. Comparative genomics analyses and searches of the natural product chemistry literature indicated that other streptomycetes may produce AHFCAs, suggesting that they could form a general class of antibiotic biosynthesis inducers in Streptomyces species, with analogous functions to the better known ␥-butyrolactone regulatory molecules.L ow-molecular-weight diffusible molecules produced by microorganisms are able to trigger such activities as secondary metabolism, morphological development, and other specialized ecological responses (1, 2). The major characterized classes of these so-called autoregulators are the acylhomoserine lactones (AHLs) in Gram-negative bacteria and the ␥-butyrolactones (GBLs) in Gram-positive Streptomyces bacteria, which are an outstanding source of medically useful natural products (3, 4). GBLs are often involved in the regulation of secondary metabolism and morphological development in Streptomyces. A-factor (compound 1) (Fig. 1A), which induces production of the antibiotic streptomycin and morphological differentiation in Streptomyces griseus, was the first GBL to be discovered and has been the most investigated to date (5). Recently, the butenolide synthase AfsA was definitively shown to be the key enzyme in A-factor biosynthesis (6).Streptomyces coelicolor A3(2), a model streptomycete, produces at least 7 closely related GBLs (7-10). SCB1 (compound 2) (Fig. 1 A), the most studied of these GBLs, appears to function mainly in the transcriptional regulation of a gene cluster proposed to direct production of an unknown polyketide metabolite (7,(11)(12)(13)(14). The S. coelicolor chromosome contains 1 homologue of afsA called scbA, which is located adjacent to the cryptic modular polyketide synthase gene cluster (13) and is required for the biosynthesis of GBLs (15). Another afsA-like gene, mmfL, is located within the linear plasmid SCP1 adjacent to the Mm antibiotic biosynthetic gene cluster (16,17). The mmfL gene product (353 amino acids) shares 43% similarity and 26% identity over 312 amino acids with ScbA. The putative A-factorlike m...

Regulation of Lankamycin Biosynthesis inStreptomyces rocheiby Two SARP Genes,srrYandsrrZ

“…30) In fact, signaling molecules with a furan ring were isolated from S. coelicolor, which induced methylenomycin production in place of GB molecules. 31) All of these results again indicate the diversity of regulatory systems for secondary metabolism in Streptomyces.…”

Molecular Regulation of Antibiotic Biosynthesis in Streptomyces

“…The autoregulator SCB1 (240) is one of several gamma-butyrolactone congeners whose synthesis involves three genes linked to the 19-gene cluster for biosynthesis of a structurally incompletely characterized yellow antibiotic (S. coelicolor polyketide [CPK]) (41,42,294). Methylenomycin furans (MMFs) are autoregulators that control MM biosynthesis, and they are made by a pathway resembling that of gamma-butyrolactones that involves three biosynthetic and two regulatory genes next to the MM biosynthetic cluster (58). (B) Autoregulatory molecules from other streptomycetes.…”

“…In this case, however, the autoregulator is not a gammabutyrolactone; instead, it is a mixture of furans (methylenomycin furans [MMFs] such as that shown in Fig. 1), made by a pathway closely similar to that of GBLs (58). The regulatory cascade is complicated by the presence of genes for two ArpA-like proteins (60).…”

The TetR Family of Regulators

“…The TFR ArpA is the A-factor receptor in S. griseus and is part of a large group of closely related TFRs (Fig. 10) that bind GBLs and related signaling molecules such as avenolide from Streptomyces avermitilis (127) and the methylenomycin furans from S. coelicolor (128). In some cases, such as that of ArpA in S. griseus, GBL signaling plays a major role in both antibiotic production and morphological development (9).…”