Studies have shown that the MscL pore expands to ~30Å in diameter when closed, with change of 15-16Å upon opening, which is the largest known conformational change in channel proteins. This large change accounts for the opening of the 30Å diameter pore, resulting in a 20 nm2 in-plane protein expansion. Such a transformation is responsible for MscL's unitary conductance of 3nS and the channel's lack of selectivity, allowing any particles with a molecular weight smaller than ~1,000. This property of MscL fulfills its role as an emergency valve to release solutes under osmotic shock.