Light induced structural changes of a full-length protein and its BLUF domain in YcgF(Blrp), a blue-light sensing protein that uses FAD (BLUF).
Blue-light sensing proteins that use FAD (BLUF) are members of a blue-light receptor family that is widely distributed among microorganisms. The Escherichia coli YcgF protein is a BLUF protein consisting of the N-terminal FAD-binding hold (BLUF domain) and the C-terminal EAL domain. The EAL domain of YcgF is predicted to have cyclic-di-GMP phosphodiesterase activity. Light-induced structural changes for the signaling state formation were studied using the light-induced Fourier transform infrared (FTIR) difference spectroscopy of both the full-length YcgF protein (YcgF-Full) and its BLUF domain (YcgF-BLUF). YcgF-Full and YcgF-BLUF showed identical UV-visible absorption spectra of flavin in the dark state and a light-induced absorption red shift for the signaling state, which relaxed to the dark state showing identical kinetics. The light-induced FTIR difference spectrum of YcgF-Full, however, was markedly different from that of YcgF-BLUF. The spectrum of YcgF-BLUF lacked most of the IR bands that were induced in the YcgF-Full spectrum. These bands were assigned to the light-induced structural changes of the protein. However, the bands for the C4=O stretching of a FAD isoalloxazine ring were induced at the same frequency with the same band intensity in the spectra for YcgF-Full and YcgF-BLUF. Furthermore, the YcgF-Full spectrum resembled that of the YcgF-BLUF when illuminated at medium-low temperatures because of the selective suppression of protein bands. The possibility that full-length-specific protein bands are predominantly ascribed to structural changes of the C-terminal EAL domain in the signaling state as a consequence of light excitation of the N-terminal BLUF domain is discussed.
Laboratory for Photobiology (1), RIKEN Photodynamics Research Center, The Institute of Physical and Chemical Research, 519-1399, Aoba, Sendai 980-0845, Japan. kojihase@riken.jp
Koji
K
Hasegawa
Shinji
S
Masuda
Taka-aki
TA
Ono
D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry*; D005182:Flavin-Adenine Dinucleotide / Q000737:chemistry* / Q000378:metabolism; D005420:Flavoproteins / Q000737:chemistry / Q000378:metabolism; D008027:Light; D010727:Phosphoric Diester Hydrolases / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000502:physiology; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013329:Structure-Activity Relationship; D013696:Temperature
C116785:AppA protein, Rhodobacter sphaeroides; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D005420:Flavoproteins; D005182:Flavin-Adenine Dinucleotide; D010727:Phosphoric Diester Hydrolases; C510176:bluF protein, E coli