Structural fold, conservation and Fe(II) binding of the intracellular domain of prokaryote FeoB.
FeoB is a G-protein coupled membrane protein essential for Fe(II) uptake in prokaryotes. Here, we report the crystal structures of the intracellular domain of FeoB (NFeoB) from Klebsiella pneumoniae (KpNFeoB) and Pyrococcus furiosus (PfNFeoB) with and without bound ligands. In the structures, a canonical G-protein domain (G domain) is followed by a helical bundle domain (S-domain), which despite its lack of sequence similarity between species is structurally conserved. In the nucleotide-free state, the G-domain's two switch regions point away from the binding site. This gives rise to an open binding pocket whose shallowness is likely to be responsible for the low nucleotide-binding affinity. Nucleotide binding induced significant conformational changes in the G5 motif which in the case of GMPPNP binding was accompanied by destabilization of the switch I region. In addition to the structural data, we demonstrate that Fe(II)-induced foot printing cleaves the protein close to a putative Fe(II)-binding site at the tip of switch I, and we identify functionally important regions within the S-domain. Moreover, we show that NFeoB exists as a monomer in solution, and that its two constituent domains can undergo large conformational changes. The data show that the S-domain plays important roles in FeoB function.
Hung
Kuo-Wei
KW
Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, ROC.
Chang
Yi-Wei
YW
Eng
Edward T
ET
Chen
Jai-Hui
JH
Chen
Yi-Chung
YC
Sun
Yuh-Ju
YJ
Hsiao
Chwan-Deng
CD
Dong
Gang
G
Spasov
Krasimir A
KA
Unger
Vinzenz M
VM
Huang
Tai-Huang
TH
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D027682:Cation Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D005296:Ferrous Compounds / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D007711:Klebsiella pneumoniae / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D020027:Pyrococcus furiosus / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D040681:Structural Homology, Protein
D001426:Bacterial Proteins; D027682:Cation Transport Proteins; D005296:Ferrous Compounds; D011994:Recombinant Proteins; D019204:GTP-Binding Proteins