Biochemical Characterization of AtHMA6/PAA1, a Chloroplast Envelope Cu(I)-ATPase

Abstract

Background: There is a lack of biochemical characterization of plant P IB-1 -type ATPases (copper transporters). Result: Phosphorylation assays show that the plant P-type ATPase PAA1 is activated by monovalent ions Cu ϩ /Ag

Functional and Biochemical Characterization of Cucumber Genes Encoding Two Copper ATPases CsHMA5.1 and CsHMA5.2

“…Cu-ATPase activities of CsHMA5.1 or CsHMA5.2 were assayed in the presence of DTT, Na 2 SO 3 , BCS, and cysteine to establish which form of CuCl, or copper thiolate, is required for ATP hydrolysis mediated by cucumber pumps. DTT and Na 2 SO 3 act as reducing agents generating Cu ϩ in the assay, whereas BCS chelates monovalent copper, and thus the amount of available Cu ϩ in the reactions containing BCS instead of Na 2 SO 3 is markedly reduced (12). Cysteine was previously shown to positively affect P 1B -ATPase activity, probably through the binding of metal and forming a chelated complex interacting with the binding domains of a heavy metal transporter (35,39,40).…”

“…ATPase and Transport Activity of CsHMA5.1 and CsHMA5.2-Copper ATPases characterized so far, CopA, ATP7A, ATP7B, and PAA1/HMA6, required monovalent copper for maximal activation of their ATPase activity (12,(35)(36)(37)(38). To establish whether copper or other metals are essential for CsHMA5.1-mediated and CsHMA5.2-mediated ATP hydrolysis, we studied the ATPase activity in vacuolar membranes isolated from the ⌬ycf1 strain expressing CsHMA5.1-GFP or CsHMA5-GFP.…”

“…A similar protein from barley (Hordeum vulgaris), HvHMA1, was shown to be involved in mobilization of zinc and copper from plastids under zinc or copper deficiency or from the intracellular compartments of the mineral storage site of grains (aleurone cells) during grain filling and germination (10). In comparison, the P 1B1 subgroup of plant P 1B -ATPases includes proteins that are highly specific for monovalent Cu ϩ (11,12). The first characterized plant HMA, AtHMA7 (RAN1), is a major component of the plant hormone ethylene signaling pathway because it delivers copper to the secretory pathway to supply the formation of functional copper-dependent ethylene receptors (13,14).…”

“…The first characterized plant HMA, AtHMA7 (RAN1), is a major component of the plant hormone ethylene signaling pathway because it delivers copper to the secretory pathway to supply the formation of functional copper-dependent ethylene receptors (13,14). Chloroplast-localized HMA6 (PAA1) and HMA8 (PAA2) are responsible for the import of copper to the chloroplasts to provide the cofactor for copper-dependent activities, antioxidant enzyme CuZn-superoxide dismutase and plastocyanin, involved in photosynthesis (12,15,16). Contrary to AtHMA6 -AtHMA8, which deliver copper to the target proteins, AtHMA5 appears to be involved in detoxification of Arabidopsis roots from copper excess (17).…”

Influence of Soil Chemistry and Plant Physiology in the Phytoremediation of Cu, Mn, and Zn

“…AtFRO7 (expressed in the chloroplasts) and AtFRO3/8 (expressed in the mitochondria) play a central role in Fe reduction, and it is hypothesized that they also participate in Cu reduction (Jeong and Connolly, 2009). AtHMA6 (or PAA1), localized in the inner chloroplast envelope, is responsible for the delivery of Cu to chloroplasts (Catty et al, 2011). AtHMA8 (PAA2), closely related to AtHMA6 (PAA1), is expressed in the thylakoid membrane and supplies Cu to plastocyanin (Tapken et al, 2012).…”