Recombinant Mouse Pro-EMAP-II Protein, CF

EMAP-II (endothelial monocyte-activating polypeptide II; also AIMP1 and SCYE1) is a 23 kDa polypeptide originally identified in the supernatant of TNF-alpha treated Meth-A fibrosarcoma cells (1, 2). In addition to EMAP-I/S100C and EMAP-III/VEGF, EMAP-II was one of three molecules presumed to enhance TNF-alpha -induced tissue factor expression on endothelial cells. Pro-EMAP-II, otherwise known as p43, is the 310 amino acid (aa) precursor to EMAP-II (3). It is considered to have widespread, if not ubiquitous expression, and is found both intra- and extracellularly (1, 4, 5). Pro-EMAP-II contains no canonical signal sequence. It does possess a 144 aa N-terminus that is characterized by the presence of two coiled-coil regions (aa 6 - 77) and two heparin-binding motifs (aa 71 - 73 and 120 - 122) (6, 7, 8). The C-terminal 166 aa are synonymous with EMAP‑II. This region binds t-RNA (5, 8). Although Pro‑EMAP‑II is 34 kDa in size, it can run anomalously in SDS-page at 43 - 44 kDa (1, 5, 9, 10). When secreted, Pro-EMAP-II circulates as either a dimer or higher-order oligomer, likely due to its coiled-coil region (5). Mouse Pro-EMAP-II shares 89% and 86% aa identity with rat and human Pro-EMAP-II, respectively, and is known to be active on human cells (3, 11). Within the cell, Pro-EMAP-II is one of eleven subunits that constitute the mammalian multisynthetase complex. This is essential for ribosomal protein synthesis (12). When cells are stressed, they dissociate Pro-EMAP-II from this complex and release it (1, 10, 13). Although the particulars are unclear, it would appear that secreted Pro-EMAP-II binds to cell surface ATP synthase alpha-subunits (14). Here, it presumably either acts as a cytokine, or undergoes proteolytic cleavage, first by MMPs at Pro108 (based on human), and later by cathepsin L at Ser145 (10, 15). The cleavage products are monomers and likely not active cytokines (5, 10, 14). In theory, Pro-EMAP-II acts as a mediator of tissue restructuring. Upon cell stress (and subsequent apoptosis), Pro-EMAP-II is released and establishes an environment where phagocytic cells can migrate to, and actively remove, dying cells and cellular debris (1, 5, 10, 13, 16).