Biochemical and genetic analyses of yeast and human high affinity copper transporters suggest a conserved mechanism for copper uptake.
The redox active metal copper is an essential cofactor in critical biological processes such as respiration, iron transport, oxidative stress protection, hormone production, and pigmentation. A widely conserved family of high affinity copper transport proteins (Ctr proteins) mediates copper uptake at the plasma membrane. However, little is known about Ctr protein topology, structure, and the mechanisms by which this class of transporters mediates high affinity copper uptake. In this report, we elucidate the topological orientation of the yeast Ctr1 copper transport protein. We show that a series of clustered methionine residues in the hydrophilic extracellular domain and an MXXXM motif in the second transmembrane domain are important for copper uptake but not for protein sorting and delivery to the cell surface. The conversion of these methionine residues to cysteine, by site-directed mutagenesis, strongly suggests that they coordinate to copper during the process of metal transport. Genetic evidence supports an essential role for cooperativity between monomers for the formation of an active Ctr transport complex. Together, these results support a fundamentally conserved mechanism for high affinity copper uptake through the Ctr proteins in yeast and humans.
Puig
Sergi
S
Department of Biological Chemistry University of Michigan Medical School, Ann Arbor, Michigan 48109-0606, USA.
Lee
Jaekwon
J
Lau
Miranda
M
Thiele
Dennis J
DJ
D000595:Amino Acid Sequence; D027682:Cation Transport Proteins; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003300:Copper / Q000378:metabolism*; D000079923:Copper Transporter 1; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010101:Oxygen Consumption; D010449:Peptide Mapping; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment
C490078:CTR1 protein, S cerevisiae; D027682:Cation Transport Proteins; D000079923:Copper Transporter 1; D008565:Membrane Proteins; C490079:SLC31A1 protein, human; D029701:Saccharomyces cerevisiae Proteins; D003300:Copper; D008715:Methionine