Fig. 1.

Composition of Mbn operons. Mbn operons can be subdivided into six groups on the basis of operon content, precursor peptide (MbnA) sequence, and phylogenetic analysis of MbnA, MbnB, and MbnC, which are present in all operons. The number of complete operons of a given type is presented to the right of the operon. Ms. trichosporium OB3b belongs to group I, Mc. parvus OBBP has both a group I and a group IIb operon, and Mc. hirsuta CSC1 has a group IIa operon. Although genes related to Mbn biosynthesis, regulation, and transport are present in all operons, genes for the putative Mbn exporter, MbnM, and importer, MbnT, are notably widespread.