Metallochaperones and metal-transporting ATPases: a comparative analysis of sequences and structures.
A comparative structural genomic analysis of a new class of metal-trafficking proteins can provide insights into the intracellular chemistry of reactive cofactors such as copper and zinc. Starting from the sequences of the metallochaperone Atx1 and from the first soluble domain of the copper-transporting ATPase Ccc2, both from yeast, a search on the available genomes was performed using a homology criterion and a metal-binding motif x'-x"-C-x'''-x''''-C. By limiting ourselves to 20% identity with any of the proteins found, several soluble copper-transport proteins were identified, as well as soluble domains of membrane-bound ATPases. Structural models were calculated using high-resolution solution structures as templates, and the models were validated using statistical and energy criteria. Residue conservation and substitution have been interpreted and discussed in terms of structure-function relationship. The potential energy surfaces have been analyzed in terms of protein-protein interactions. We find that metallochaperones and their physiological partner ATPases from several phylogenetic kingdoms recognize one another, via an interplay of electrostatics, hydrogen bonding, and hydrophobic interactions, in a manner that precisely orients the metal-binding side chains for rapid metal transfer between otherwise tight binding sites. Finally, other putative metal-transport proteins are mentioned that have low homology and/or a different metal-binding consensus motif and that appear to use similar structures for recognition and transfer. This analysis highlights the wealth and the complexity of the field.
Arnesano
Fabio
F
Magnetic Resonance Center CERM and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019, Sesto Fiorentino, Florence, Italy.
Banci
Lucia
L
Bertini
Ivano
I
Ciofi-Baffoni
Simone
S
Molteni
Elena
E
Huffman
David L
DL
O'Halloran
Thomas V
TV
D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000378:metabolism*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D019216:Metals, Heavy / Q000378:metabolism*; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020539:Sequence Analysis, Protein / Q000379:methods; D017386:Sequence Homology, Amino Acid
D002352:Carrier Proteins; D019216:Metals, Heavy; D018832:Molecular Chaperones; D000251:Adenosine Triphosphatases