2FMJ:
reference: Conversion of trypsin into a Na(+)-activated enzyme., Page MJ, Bleackley MR, Wong S, MacGillivray RT, Di Cera E, Biochemistry. 2006 Mar 7;45(9):2987-93. PMID: 16503653

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).