Abstract
Non-ribosomal peptide synthetases (NRPSs) are large multienzyme machineries. They synthesize numerous important natural products starting from amino acids. For peptide synthesis functionally specialized NRPS modules interact in a defined manner. Individual modules are either located on a single or on multiple different polypeptide chains. The “peptide-antimicrobial-Xenorhabdus” (PAX) peptide producing NRPS PaxS from Xenorhabdus bacteria consists of the three proteins PaxA, PaxB and PaxC. Different docking domains (DDs) located at the N-termini of PaxB and PaxC and at the C-termini of PaxA and BaxB mediate specific non-covalent interactions between them. The N-terminal docking domains precede condensation domains while the C-terminal docking domains follow thiolation domains. The binding specificity of individual DDs is important for the correct assembly of multi-protein NRPS systems. In many multi-protein NRPS systems the docking domains are sufficient to mediate the necessary interactions between individual protein chains. However, it remains unclear if this is a general feature for all types of structurally different docking domains or if the neighboring domains in some cases support the function of the docking domains. Here, we report the 1H, 13C and 15 N NMR resonance assignments for a C-terminal di-domain construct containing a thiolation (T) domain followed by a C-terminal docking domain (CDD) from PaxA and for its binding partner – the N-terminal docking domain (NDD) from PaxB from the Gram-negative entomopathogenic bacterium Xenorhabdus cabanillasii JM26 in their free states and for a 1:1 complex formed by the two proteins. These NMR resonance assignments will facilitate further structural and dynamic studies of this protein complex.
Highlights
Non-ribosomal peptide synthases (NRPS) use amino acids as building blocks for the synthesis of complex natural products
The T domain is followed by a condensation domain (C) which catalyses the formation of peptide bonds between the amino acid bound to the T domain of its own module and an amino acid or a peptide chain bound to the T domain of the downstream module
For many types of docking domains (DDs) interactions it has been experimentally demonstrated that the DDs act independently from the other functional domains in an NRPS or polyketide synthase (PKS) in order to mediate the non-covalent interactions between protein chains needed for the functional assembly of functional megasynthase complexes (Dorival et al 2016; Hacker et al 2018)
Summary
Non-ribosomal peptide synthases (NRPS) use amino acids as building blocks for the synthesis of complex natural products. In multi-protein NRPS systems specific noncovalent interactions between the individual protein chains determine the functional assembly of the NRPS complex and thereby the order of amino acids in the synthesized peptide. For many types of DD interactions it has been experimentally demonstrated that the DDs act independently from the other functional domains in an NRPS or PKS in order to mediate the non-covalent interactions between protein chains needed for the functional assembly of functional megasynthase complexes (Dorival et al 2016; Hacker et al 2018). The T1-CDD (amino acids 981–1084 of PaxA) comprises 104 amino acids (12 kDa), whereas the NDD (amino acids 1–30 of PaxB) contains only 30 amino acids (3.6 kDa)
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