P(1B)-type ATPases transport heavy metals (Cu+, Cu2+, Zn2+, Co2+, Cd2+, Pb2+) across membranes. Present in most organisms, they are key elements for metal homeostasis. P(1B)-type ATPases contain 6-8 transmembrane fragments carrying signature sequences in segments flanking the large ATP binding cytoplasmic loop. These sequences made possible the differentiation of at least four P(1B)-ATPase subgroups with distinct metal selectivity: P(1B-1): Cu+, P(1B-2): Zn2+, P(1B-3): Cu2+, P(1B-4): Co2+. Mutagenesis of the invariant transmembrane Cys in H6, Asn and Tyr in H7 and Met and Ser in H8 of the Archaeoglobus fulgidus Cu+-ATPase has revealed that their side chains likely coordinate the metals during transport and constitute a central unique component of these enzymes. The structure of various cytoplasmic domains has been solved. The overall structure of those involved in enzyme phosphorylation (P-domain), nucleotide binding (N-domain) and energy transduction (A-domain), appears similar to those described for the SERCA Ca2+-ATPase. However, they show different features likely associated with singular functions of these proteins. Many P(1B)-type ATPases, but not all of them, also contain a diverse arrangement of cytoplasmic metal binding domains (MBDs). In spite of their structural differences, all N- and C-terminal MBDs appear to control the enzyme turnover rate without affecting metal binding to transmembrane transport sites. In addition, eukaryotic Cu+-ATPases have multiple N-MBD regions that participate in the metal dependent targeting and localization of these proteins. The current knowledge of structure-function relationships among the different P(1B)-ATPases allows for a description of selectivity, regulation and transport mechanisms. Moreover, it provides a framework to understand mutations in human Cu+-ATPases (ATP7A and ATP7B) that lead to Menkes and Wilson diseases.

Plant microbiome and its manipulation herald a new era for plant biotechnology with the potential to benefit sustainable crop production. However, studies evaluating the diversity, structure and impact of the microbiota in economic important crops are still rare. Here we describe a comprehensive inventory of the structure and assemblage of the bacterial and fungal communities associated with sugarcane. Our analysis identified 23,811 bacterial OTUs and an unexpected 11,727 fungal OTUs inhabiting the endophytic and exophytic compartments of roots, shoots, and leaves. These communities originate primarily from native soil around plants and colonize plant organs in distinct patterns. The sample type is the primary driver of fungal community assemblage, and the organ compartment plays a major role in bacterial community assemblage. We identified core bacterial and fungal communities composed of less than 20% of the total microbial richness but accounting for over 90% of the total microbial relative abundance. The roots showed 89 core bacterial families, 19 of which accounted for 44% of the total relative abundance. Stalks are dominated by groups of yeasts that represent over 12% of total relative abundance. The core microbiome described here comprise groups whose biological role underlies important traits in plant growth and fermentative processes.

As in other P-type ATPases, metal binding to transmembrane metal-binding sites (TM-MBS) in Cu ؉ -ATPases is required for enzyme phosphorylation and subsequent transport. However, Cu ؉ does not access Cu ؉ -ATPases in a free (hydrated) form but is bound to a chaperone protein. CopA ͉ CopZ ͉ Cu homeostasis ͉ Cu-ATPase ͉ metal binding C opper is an essential cofactor in many biological processes (1). However, it also participates in harmful Fenton reactions. Consequently, Cu is ''buffered'' at a ''no-free Cu'' level by metallothioneins and chaperones with binding constants for Cu ϩ in the picomolar-femtomolar range (2, 3). Within these constraints, Cu ϩ chaperones route Cu ϩ to various intracellular targets, and Cu ϩ transmembrane transport systems maintain the total copper quota within the 10-100 M range (1-4). How the Cu ϩ chaperones transfer the metal to and from transmembrane transport sites is a central feature of transmembrane Cu ϩ transport. To better understand these phenomena, we have studied the delivery of Cu ϩ by the Archaeoglobus fulgidus Cu ϩ chaperone, CopZ, to the corresponding Cu ϩ -ATPase, CopA.CopA is a member of the P 1B subgroup of P-type ATPases (5-7). Cu ϩ -ATPases are essential to maintain Cu ϩ homeostasis. For instance, mutations in the two Cu ϩ -ATPase genes present in humans, ATP7A and ATP7B, lead to Menkes syndrome and Wilson's disease, respectively (8, 9). The Cu ϩ -ATPases transport cycle follows the classical E1/E2 Albers-Post model (10-12). Catalytic phosphorylation of the enzyme in the E1 conformation occurs upon binding of cytoplasmic metal to transmembrane metal-binding sites (TM-MBS) and ATP binding with high affinity (l M) to the ATP-binding domain (ATP-BD) (Fig. 1). It is assumed that upon phosphorylation, Cu ϩ is occluded within the transmembrane region. The subsequent conformational change allows metal deocclusion and release to the extracellular (vesicular/luminal) compartment followed by enzyme dephosphorylation and return to the E1 form (10). Functional studies of various Cu ϩ -ATPases have characterized the Cu ϩ transport, Cu ϩ -dependent ATPase activity, phosphorylation, and dephosphorylation partial reactions (5,(13)(14)(15)(16)(17)(18)(19).Cu ϩ -ATPases consist of eight transmembrane segments, two large cytosolic loops comprising the A-domain and the ATP-BD, and regulatory metal-binding domains (MBDs) in their N terminus (6, 8-10, 20, 21) (Fig. 1). A. fulgidus CopA has an atypical