Structural approach to a novel tandem repeat DNA-binding domain, STPR, by CD and NMR.
Fibroin-modulator-binding protein 1 (FMBP-1) is a factor that binds the transcriptional activation elements of the fibroin gene. It has a novel structure, consisting of four tandem repeats (R1-R4) of 23 amino acids each in the C-terminal half. This region is referred to as the STPR (score and three amino acid peptide repeat) domain and acts as a DNA-binding domain in FMBP-1. Interestingly, the homology among the four repeats is remarkably high. Here, we have determined the three-dimensional structures of the four repeats by NMR. All four repeat units have basically the same structure: a short alpha-helix in the N-terminal half maintained by a salt bridge and an N-capping box. CD studies showed that the full-length STPR domain was 31% helical in solution. This is explained by the connections among the four short helices that were determined separately by NMR. From the thermal-denaturation study, it can be deduced that these four helices in the full-length STPR domain moved flexibly with no interaction among them. However, the specific DNA caused a distinct increase, of up to 76%, in the alpha-helical content of the full-length STPR domain. This finding suggests that the binding of the full-length STPR domain to specific DNA causes an induced-fit conformational change that increases alpha-helicity; the poorly structured regions of the protein may form a regular secondary structure. Furthermore, the mutation analysis showed that the four repeats of the STPR domain raise the possibility of interaction with DNA in different ways.
Saito
Shin
S
Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
Aizawa
Tomoyasu
T
Kawaguchi
Kyosuke
K
Yamaki
Takeshi
T
Matsumoto
Daisuke
D
Kamiya
Masakatsu
M
Kumaki
Yasuhiro
Y
Mizuguchi
Mineyuki
M
Takiya
Sigeharu
S
Demura
Makoto
M
Kawano
Keiichi
K
D000595:Amino Acid Sequence; D000818:Animals; D012831:Bombyx; D002942:Circular Dichroism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D005349:Fibroins / Q000235:genetics*; D019476:Insect Proteins / Q000737:chemistry* / Q000235:genetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020449:Repetitive Sequences, Amino Acid; D017386:Sequence Homology, Amino Acid; D012996:Solutions; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics
D004268:DNA-Binding Proteins; D019476:Insect Proteins; D012996:Solutions; D014157:Transcription Factors; D005349:Fibroins