Roads to Rome: Role of Multiple Cassettes in Cyanobactin RiPP Biosynthesis.

Area of Science:

• Biochemistry
• Natural Product Biosynthesis
• Molecular Biology

Background:

• Ribosomally synthesized and post-translationally modified peptides (RiPPs) are natural products derived from precursor peptides modified by enzymes.
• While typically one product arises from a precursor, some RiPP pathways, like cyanobactins, feature multiple bioactive products encoded by a single precursor, flanking recognition sequences called cassettes.
• The function of these multiple cassettes has been unclear but suggests biosynthetic flexibility.

Purpose of the Study:

• To investigate the role of multiple cassettes in cyanobactin biosynthesis.
• To determine if multiple cassettes confer unique processing characteristics to RiPP pathways.
• To propose a hallmark feature for multicassette RiPPs based on enzyme processing.

Main Methods:

• Analysis of cyanobactin biosynthetic pathway.
• Characterization of TruD heterocyclase activity.
• Enzyme processing assays.

Main Results:

• The presence of multiple cassettes in cyanobactin biosynthesis leads to distributive enzyme processing across multiple pathway steps.
• TruD heterocyclase demonstrates stochastic and distributive activity.
• The enzyme accepts various biosynthetic routes, not just a canonical one, with certain substrates.

Conclusions:

• Distributive enzyme processing is a proposed hallmark of multicassette RiPPs.
• This processing equalizes cassette modification, enhancing pathway plasticity.
• The pathway's flexibility enables access to a wider range of chemical diversity.