Structural basis for metal binding specificity: the N-terminal cadmium binding domain of the P1-type ATPase CadA.
In bacteria, P1-type ATPases are responsible for resistance to di- and monovalent toxic heavy metals by taking them out of the cell. These ATPases have a cytoplasmic N terminus comprising metal binding domains defined by a betaalphabetabetaalphabeta fold and a CXXC metal binding motif. To check how the structural properties of the metal binding site in the N terminus can influence the metal specificity of the ATPase, the first structure of a Cd(II)-ATPase N terminus was determined by NMR and its coordination sphere was investigated by X-ray absorption spectroscopy. A novel metal binding environment was found, comprising the two conserved Cys residues of the metal binding motif and a Glu in loop 5. A bioinformatic search identifies an ensemble of highly homologous sequences presumably with the same function. Another group of highly homologous sequences is found which can be referred to as zinc-detoxifying P1-type ATPases with the metal binding pattern DCXXC in the N terminus. Because no carboxylate groups participate in Cu(I) or Ag(I) binding sites, we suggest that the acidic residue plays a key role in the coordination properties of divalent cations, hence conferring a function to the N terminus in the metal specificity of the ATPase.
Banci
Lucia
L
Magnetic Resonance Center CERM and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence, Italy.
Bertini
Ivano
I
Ciofi-Baffoni
Simone
S
Su
Xun-Cheng
XC
Miras
Roger
R
Bal
Nathalie
N
Mintz
Elisabeth
E
Catty
Patrice
P
Shokes
Jacob E
JE
Scott
Robert A
RA
D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001051:Apoenzymes / Q000737:chemistry / Q000378:metabolism; D001693:Biological Transport, Active; D002104:Cadmium / Q000737:chemistry / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics; D002413:Cations, Divalent / Q000737:chemistry / Q000378:metabolism; D000073840:Copper-Transporting ATPases; D018360:Crystallography, X-Ray; D019281:Dimerization; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D008089:Listeria monocytogenes / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012996:Solutions; D013816:Thermodynamics
D001051:Apoenzymes; D027682:Cation Transport Proteins; D002413:Cations, Divalent; D012996:Solutions; D002104:Cadmium; D000251:Adenosine Triphosphatases; C109898:Zn(II)-translocating P-type ATPase; C059771:cadmium translocating ATPase; D000073840:Copper-Transporting ATPases