Copper Transporters: CTR1, CTR2, ATP7A, & ATP7B Veronica Lopez Stefano Pineda Jude Okolo

Copper and Copper Transporters Useful because of its ability to reduce to Copper( I) from Copper(II) Functions in processes such as mitochondrial respiration, iron transport, hormone production, neurotransmitter synthesis, and pigmentation. Copper transporters maintain homeostasis of copper levels at the cellular level Many copper transporters focus here on CTR1 CTR5, ATP7A, and ATP7B

Menkes Syndrome and Wilson Disease Menkes syndrome X-linked recessive disorder defective ATP7A – Characterized by copper deficiency Menkes affects delivery of copper to the brain and incorporation of copper in different enzymes Symptoms include decreased neural development, seizures, and connective tissue abnormalities Wilson Disease autosomal recessive disease causes defect in ATP7B Characterized by copper overload Wilson causes toxic accumulation of copper in the brain by decreased copper excretion by the liver into the bile Symptoms include hepatic abnormalities leading to liver failure, neurological defects, and psychiatric symptoms

Human CTR1 and CTR2

CTR1 and CTR2: Primary Structure YCTR1 and CTR2 have 25% homology and are most similar in the three transmembrane regions CTR1 has an amino terminal region rich in Met and His and an MXXXM motif in TM2 Both CTR1 and CTR2 have a Met 20 AAs upstream from TM1 CTR1 made up of 190 amino acids CTR2 is made up of slightly less.

CTR1 and CTR2: Secondary Structure CTR proteins in general have three transmembrane α-helices. N-terminus is located in the extracellular space C-terminus is located in intracellular space CTR2 lacks the extended N-terminus of CTR1and the Met motifs may be the cause of decreased affinity for copper transport GG4 motif has role in helix-helix interactions in other proteins. Based on their transmembrane amino acid sequence CTR proteins in general have three transmembrane α-helices. N-termini are located in the extracellular space GG4 motif has also been shown to play vital role in helix-helix interactions in other proteins.

Model for the primary structure of Ctr high affinity copper transport proteins. Model for the primary structure of Ctr high affinity copper transport proteins. Alignment of copper transport proteins from S. cerevisiae (ScCtr1, ScCtr3), S. pombe (SpCtr4, SpCtr5), human and mouse (h/mCtr1), and A. thaliana (AtCopt1). Conserved features in the primary structure are represented from the amino terminus (left) to carboxyl terminus (right). All proteins contain three putative transmembrane domains (TMD1–3) shown in black. With the exception of yeast Ctr3, all members of the Ctr family of copper transporters contain putative copper binding motifs, called Mets motifs (gray boxes), consisting of 3–5 methionine residues arranged as MXXM and/or MXM. Yeast and human Ctr1 proteins contain eight and two Mets motifs, respectively. Other conserved features, Ctr1 Met-127 and the MXXXM motif in TMD2, are represented in black and whitecharacters, respectively. The length of each protein in amino acids is shown on the right. Puig S et al. J. Biol. Chem. 2002;277:26021-26030 ©2002 by American Society for Biochemistry and Molecular Biology

CTR1: Tertiary and Quaternary Structure CTR1 proteins monomers consist of three transmembrane domains (TMD) Each monomer makes up a homotrimer to form a copper transport core. TMD2 and TMD3 have MXXXM and GXXXG motifs The Met motif in TMD2 may play a role in copper sensing and uptake. GG4 motif essential to formation of functional copper uptake proteins. TMD2 and TMD3 have MXXXM and GXXXG motifs The Met motif in TMD2 may play a role in copper sensing and uptake. The GG4 motif is essential to formation of fully functional copper uptake proteins.

Human CTR1

CTR2: Tertiary and Quaternary Structure CTR2 protein has three transmembrane domains Monomers exist as homomultimers Much less in known about CTR2

ATP 7A

ATP7A and ATP7B: Primary Structure Overall structure of ATP7A and 7B is very similar Main difference is in first four of six membrane binding domains (MBD) This diversity could be responsible for different trafficking behavior in ATP7A and ATP7B Primary sequence homology is 50-60% ATP7A is made up of 1480AA ATP7B is made up of 1465AA The six MBD of the N-terminus of ATP7A and ATP7B is 600 residues long and has the MXCXXC copper binding motif The M-domain of the three of the transmembrane helices have residues that coordinate with copper Helix 6 has the Cys-Pro-Cys motif Helix 7 has the Asp-Tyr motif Helix 8 has Met-X-X-Ser motif

ATP7A and ATP7B: Secondary Structure Studies have shown ATPases to have compactly folded structures with βαββαβ-folds in the MBD segments of which there are six total Copper binding Cys residues of the CXXC are located in the βα loop and the N-terminus portion of the first α-helix ATP7A and ATP7B have eight transmembrane helices

ATP7A and ATP7B: Tertiary Structure MBD1-4 facilitate binding and hydrolysis of ATP MBD5 and 6 are necessary for copper binding in the transmembrane portion of transporter There are eight TMS in the transmembrane portion of Cu-ATPases A CPC motif in the TMS is highly conserved along with four other AA in segments 7 and 8 and are likely to form copper binding sites within the membrane. The A-Domain, P-Domain, and N-Domain all function in ATP binding and catalytic phosphorylation of ATP

Human Cu-ATPase

Comparing Copper Transport Proteins Much less is known about the structure of CTR1 and CTR2 and much more is known about ATP7A and ATP7B ATP7A and ATP7B are much more similar to one another than CTR1 and CTR2 and ATP7A and B are part of large family of P-type ATPases CTR1 and 2 function in copper import at cell membrane while ATP7A and ATP7B function in copper transport into trans Golgi network and export of Copper at the

References Van den Burghe, Peter V. E. and Klomp, Leo W. J. Posttranslational Regulation of Copper Transporters. Journal of Biological Inorganic Chemistry (2010) 15: 37-46 Lutsenko, Svetlana et.al. Function and Regulation of Copper-Transporting ATPases. The American Physiological Society (2007) 87:1011-1046 Puig, Sergi, et.al. Biochemical and Genetic Analyses of Yeast and Human High Affinity Copper Transporters Suggest a Conserved Mechanism for Copper Uptake The Journal of Biological Chemistry (2002) 29:26021-26030 De Bie, P., Muller, P., et.al. Molecular Pathogenesis of Wilson and Menkes Disease: Correlation of Mutations with Molecular Effects and Disease Phenotypes. Journal of Medical Genetics (2007) 44: 673-688