Primary and tectonic features of the Currawong Zn-Cu-Pb(-Au) massive sulfide deposit, Benambra, Victoria: Implications for ore genesis

The Late Silurian Currawong Zn-Cu-Pb(-Au) massive sulfide deposit is located in the northeastern highlands of Victoria, southeastern Australia. The Currawong deposit forms two strata-bound concordant massive sulfide lenses which have been dissected by late subvertical faulting. Each massive sulfide lens possesses a concordant stringer system in the footwall to the massive sulfides. Host rocks are comprised of subaqueous rhyodacitic to andesitic breccias and coherent volcanic rocks. The geometry and distribution of ore types in the Currawong deposit are characteristic of both sheet- and layered-type deposits as described in Australia. Mineralization is divided into six types: Pb-Zn, pyrite Zn, massive pyrite-magnetite, footwall stringer, and overprinting veins and breccias related to local remobilization of base metal sulfides during deformation. Three generations of deformation are recognized in the host stratigraphy. The internal stratigraphy, metal zonation characteristics, and primary textures, as well as the paragenesis of the ores and limited stratigraphic reconstruction, indicate that the deposit formed by sub-sea-floor replacement of unconsolidated permeable rocks rather than seafloor exhalative processes. -from Author

A helical assembly of human ESCRT-I scaffolds reverse-topology membrane scission.

The ESCRT complexes drive membrane scission in HIV-1 release, autophagosome closure, multivesicular body biogenesis, cytokinesis, and other cell processes. ESCRT-I is the most upstream complex and bridges the system to HIV-1 Gag in virus release. The crystal structure of the headpiece of human ESCRT-I comprising TSG101-VPS28-VPS37B-MVB12A was determined, revealing an ESCRT-I helical assembly with a 12-molecule repeat. Electron microscopy confirmed that ESCRT-I subcomplexes form helical filaments in solution. Mutation of VPS28 helical interface residues blocks filament formation in vitro and autophagosome closure and HIV-1 release in human cells. Coarse-grained (CG) simulations of ESCRT assembly at HIV-1 budding sites suggest that formation of a 12-membered ring of ESCRT-I molecules is a geometry-dependent checkpoint during late stages of Gag assembly and HIV-1 budding and templates ESCRT-III assembly for membrane scission. These data show that ESCRT-I is not merely a bridging adaptor; it has an essential scaffolding and mechanical role in its own right