Nonribosomal peptide synthetase; part of the gene cluster that mediates the biosynthesis of siderophore ferrichrome A which is contributing to organismal virulence (PubMed:17138696, PubMed:20070524). The first step of ferrichrome A biosynthesis is performed by the HMG-CoA synthase hcs1 which catalyzes the generation of HMG-CoA and CoA using acetoacetyl-CoA and acetyl-CoA as substrates (PubMed:20070524). The enoyl-CoA isomerase/hydratase fer4 then catalyzes the conversion of hcs1-produced HMG-CoA to methylglutaconyl-CoA (PubMed:20070524). The acyltransferase fer5 then fuses the fer4-generated methylglutaconyl-CoA with sid1-generated hydroxyornithine to yield methylglutaconyl hydroxyornithine (PubMed:20070524). Methylglutaconyl hydroxyornithine is then available for use by the NRPS fer3 to generate ferrichrome A (PubMed:20070524). Siderophore biosynthesis. Expression regulated by iron through the urbs1 transcription factor (PubMed:17138696). NRP synthetases are composed of discrete domains (adenylation (A), thiolation (T) or peptidyl carrier protein (PCP) and condensation (C) domains) which when grouped together are referred to as a single module. Each module is responsible for the recognition (via the A domain) and incorporation of a single amino acid into the growing peptide product. Thus, an NRP synthetase is generally composed of one or more modules and can terminate in a thioesterase domain (TE) that releases the newly synthesized peptide from the enzyme. Occasionally, epimerase (E) domains (responsible for l- to d- amino acid conversion) are present within the NRP synthetase. Fer3 has the following architecture: A-T-C-A-T-C-A-T-C-T-C-T-C (PubMed:20070524). The lack of corresponding A domains in the 2 last modules suggests that A domains have to be used iteratively to incorporate the six amino acids in ferrichrome A (PubMed:20070524). Impairs the production of ferrichrome A but does not affect the production of ferrichrome (PubMed:20070524). Belongs to the NRP synthetase family.