Interacts with the host receptor (By similarity). Mediates virus attachment to host TFRC. This attachment induces virion internalization predominantly through clathrin-mediated endocytosis (PubMed:17287727). Class I viral fusion protein that directs fusion of viral and host endosomal membranes, leading to delivery of the nucleocapsid into the cytoplasm. Membrane fusion is mediated by irreversible conformational changes induced upon acidification in the endosome. Stable signal peptide (SSP): cleaved and functions as a signal peptide. In addition, it is also retained as the third component of the GP complex. The SSP is required for efficient glycoprotein expression, post-translational maturation cleavage of GP1 and GP2, glycoprotein transport to the cell surface plasma membrane, formation of infectious virus particles, and acid pH-dependent glycoprotein-mediated cell fusion. Homotetramer; disulfide-linked. Homotetramer. GP2 homotetramers bind through ionic interactions with GP1 homotetramers to form the GP complex together with the stable signal peptide. The GP-C polyprotein interacts with the host protease MBTPS1/SKI-1 resulting in the polyprotein processing. Binding to the stable signal peptide masks endogenous ER localization signals in the cytoplasmic domain of G2 to ensure that only the fully assembled, tripartite GP complex is transported for virion assembly. The cytoplasmic domain of GP2 plays a role in ER location. It also contains a zinc-binding domain that allows SSP retention in the GPC complex by accepting a cysteine from SSP as the fourth ligand. Specific enzymatic cleavages in vivo yield mature proteins. GP-C polyprotein is cleaved in the endoplasmic reticulum by the host protease MBTPS1. Only cleaved glycoprotein is incorporated into virions. The SSP remains stably associated with the GP complex following cleavage by signal peptidase and plays crucial roles in the trafficking of GP through the secretory pathway. Belongs to the arenaviridae GPC protein family.