title: Serine in BLUF domains displays spectral importance in computational models.
abstract: The BLUF (blue-light sensing using flavine) domain of the AppA photoreceptor protein from Rhodobacter sphaeroides was modelled by using quantum chemical chromophore plus amino acid models at the (TD-)B3LYP/6-31G * level of theory. The models were based on NMR structures, and further refined by CHARMM force field molecular dynamics simulations. The goal is to explain the total redshift by about 10nm in the UV/Vis spectra of BLUF domains after illumination, and to relate it to structural changes. For this purpose UV/Vis spectra of the available NMR structures were calculated and related to geometrical features. In particular, the hydrogen network embedding the central chromophore is discussed. Specifically, the position of a conserved glutamine, Q63, is found to be important in agreement with findings from previous works. Additionally, however, we find a systematic dependence also on the geometry of a conserved serine, S41. Based on a series of calculations with known structures and with artificial structural models, we argue that indeed the light-induced switching of both Q63 and S41 is necessary to explain the full approximately 10nm redshift in the light (signalling) state of serine containing BLUF domains. Following or accompanying the double switching, two structurally highly important residues W104 and M106 exchange places, but do not affect the overall UV/Vis properties of the chromophore.
authors.affiliation: Theoretische Chemie, Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, D-14476 Potsdam-Golm, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Götze
authors.forename: Peter
authors.initials: P
authors.lastname: Saalfrank
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003198:Computer Simulation; D017124:Conserved Sequence; D005420:Flavoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D012242:Rhodobacter sphaeroides / Q000737:chemistry*; D016415:Sequence Alignment; D012694:Serine / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: C116785:AppA protein, Rhodobacter sphaeroides; D001426:Bacterial Proteins; D005420:Flavoproteins; D012694:Serine