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Copper is an essential micronutrient and yet is highly toxic to cells at elevated concentrations. P1B‐ATPase proteins are critical for this regulation, providing active extrusion across cellular membranes. One unique molecular adaptation of P1B‐ATPases compared to other P‐type ATPases is the presence of metal‐binding domains (MBDs) at the cytosolic termini, which however are poorly characterized with an elusive mechanistic role. Here we present the MBD architecture in metal‐free and metal‐bound forms of the archetype Cu+‐specific P1B‐ATPase LpCopA, determined using NMR. The MBD is composed of a flexible tail and a structured core with a metal ion binding site defined by three sulfur atoms, one of which is pertinent to the so‐called CXXC motif. Furthermore, we demonstrate that the MBD rather than being involved in ion delivery likely serves a regulatory role, which is dependent on the classical P‐type ATPase E1‐E2 transport mechanism. Specifically, the flexible tail appears responsible for autoinhibition while the metal‐binding core is used for copper sensing. This model is validated by a conformation‐sensitive and MBD‐targeting nanobody that can structurally and functionally replace the flexible tail. We propose that autoinhibition of Cu+‐ATPases occurs at low copper conditions via MBD‐mediated interference with the soluble domains of the ATPase core and that metal transport is enabled when copper levels rise, through metal‐induced dissociation of the MBD. This allows P1B‐ATPase ‘vacuum cleaners’ to tune their own activity, balancing the levels of critical micronutrients in the cells. [ABSTRACT FROM AUTHOR]

Immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangement (GR) studies have been successfully employed to investigate the clonality and cell lineage of various lymphoid malignancies. Several lymphoma cell lines, such as BJAB, RAJI, DG75 and Jurkat cell lines, were often used as the positive controls in GR detection assays. Of those, the DG75 B-cell lymphoma line was found to exhibit biclonality [two or more homoduplex and heteroduplex bands in a polymerase chain reaction (PCR) product of clonality assay] in the PCR of GR detection assays. To further explore these characteristics of the biclonal phenomenon, the PCR products were purified and cloned into a pEGM-T clone vector. The sequences were analyzed using DNA analysis software. The results demonstrated that the two bands originated from two forms of GR of DG75 cell lines, i.e., DG75 is a biclonal cell line in Ig GRs, which has not been reported before.