The structure and transcriptional analysis of a global regulator from Neisseria meningitidis

Neisseria meningitidis, a causative agent of bacterial meningitis, has a relatively small repertoire of transcription factors, including NMB0573 (annotated AsnC), a member of the Lrp-AsnC family of regulators that are widely expressed in both Bacteria and Archaea. In the present study we show that NMB0573 binds to l-leucine and l-methionine and have solved the structure of the protein with and without bound amino acids. This has shown, for the first time that amino acid binding does not induce significant conformational changes in the structure of an AsnC/Lrp regulator although it does appear to stabilize the octameric assembly of the protein. Transcriptional profiling of wild-type and NMB0573 knock-out strains of N. meningitidis has shown that NMB0573 is associated with an adaptive response to nutrient poor conditions reflected in a reduction in major surface protein expression. On the basis of its structure and the transcriptional response, we propose that NMB0573 is a global regulator in Neisseria controlling responses to nutrient availability through indicators of general amino acid abundance: leucine and methionine.