µsL (in blue) dimerization likely proceeds via C337 in Cµ2 (top arrow) though C575 intra-subunit bonds (in pink) may favor covalent binding via C337 (in yellow). Compact µs2L2C575OX subunits are then formed which are attacked by ERp44 (depicted in green). Polymerization proceeds by sequential recruitment of mixed ERp44- µs2L2 complexes, until fully oxidized hexamers are formed. A reduced ERp44 is released at each step. It is also possible that oxidized µs2L2 subunits (in red) bind directly to an ERp44- µs2L2 complex. E 