5ZC2

Crystal structure of the flavin reductase of Acinetobacter baumannii p-hydroxyphenylacetate 3-hydroxylase (HPAH) and identification of amino acid residues underlying its regulation by aromatic ligands

(2018) Arch Biochem Biophys 653: 24-38

• PubMed: 29940152 Search on PubMed
• DOI: https://doi.org/10.1016/j.abb.2018.06.010
• Primary Citation of Related Structures:  
  5ZC2


• PubMed Abstract: 
  

  The first step in the degradation of p-hydroxyphenylacetic acid (HPA) is catalyzed by the two-component enzyme p-hydroxyphenylacetate 3-hydroxylase (HPAH). The two components of Acinetobacter baumannii HPAH are known as C ₁ and C ₂ , respectively. C ₁ is a flavin reductase that uses NADH to generate reduced flavin mononucleotide (FMNH ^- ), which is used by C ₂ in the hydroxylation of HPA. Interestingly, although HPA is not directly involved in the reaction catalyzed by C ₁ , the presence of HPA dramatically increases the FMN reduction rate. Amino acid sequence analysis revealed that C ₁ contains two domains: an N-terminal flavin reductase domain, and a C-terminal MarR domain. Although MarR proteins typically function as transcription regulators, the MarR domain of C ₁ was found to play an auto-inhibitory role. Here, we report a crystal structure of C ₁ and small-angle X-ray scattering (SAXS) studies that revealed that C ₁ undergoes a substantial conformational change in the presence of HPA, concomitant with the increase in the rate of flavin reduction. Amino acid residues that are important for HPA binding and regulation of C ₁ activity were identified by site-directed mutagenesis. Amino acid sequence similarity analysis revealed several as yet uncharacterized flavin reductases with N- or C-terminal fusions.

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Organizational Affiliation: 

Department of Biochemistry and Center for Excellence in Protein and Enzyme Technology Faculty of Science, Mahidol University, Bangkok, 10400, Thailand.