biological unit form 1 is a hetero-hexameric ring, generated from the hetero-dimer in the asymmetric unit by the following two operations: \cf0\f1\fs22\lang1031 -Y,X-Y,Z and -X+Y,-X,Z\cf1\f0\fs18\lang1033 / biological unit form 2a is a dodecameric head-to-head assembly, generated from the hetero-dimer in the asymmetric unit by the following five operations: \cf0\f1\fs22\lang1031 -Y,X-Y,Z and -X+Y,-X,Z and Y,X,-Z and \par -X,-X+Y,-Z and X-Y,-Y,-Z\cf1\f0\fs18\lang1033 / biological unit form 2b is a dodecameric tail-to-tail assembly, generated from the hetero-dimer in the asymmetric unit by the following five operations: \cf0\f1\fs22\lang1031 -Y,X-Y,Z and -X+Y,-X,Z and Y,X,-Z+1 and \par -X,-X+Y,-Z+1 and X-Y,-Y,-Z+1\cf1\f0\fs18\lang1033