SEQUENCE CHAINS A AND B: NO SUITABLE SEQUENCE DATABASE REFERENCE WAS FOUND AT THE TIME OF ...SEQUENCE CHAINS A AND B: NO SUITABLE SEQUENCE DATABASE REFERENCE WAS FOUND AT THE TIME OF PROCESSING. CHAIN C: THE SEQUENCE LISTED IN THE SEQRES FOR CHAIN C IS THE PORTION OF THE FOLLOWING CONSTRUCT THAT WAS CLEARLY OBSERVED IN THE DENSITY: ANKLDSKKLTRSNGTTLEYSQITDADNATKAVETLKNSIKLEGSLVVGKTTVEIK EGTVTLKREIEKDGKVKVFLNDTAGSNKKTGKWEDSTSTLTISADSKKTKDLVFL TDGTITVQQYNTAGTSLEGSASEIKNLSELKNALK THE AUTHORS DO NOT KNOW IF THE PORTION OF THE CONSTRUCT THAT WAS NOT OBSERVED IN THE DENSITY WAS MISSING DUE TO PROTEOLYSIS, OR WAS DISORDERED IN THE CRYSTAL. CHAIN D: THE AUTHORS SAW AN EXTRA BETA STRAND OF DENSITY THAT WAS NOT CONTINUOUS WITH THE MAIN BODY OF DENSITY (I.E. THERE WAS NO DENSITY FOR A CONNECTING LOOP) AND THAT DID NOT SHOW CLEAR SIDECHAIN DENSITY. THIS STRAND PRESUMABLY ARISES FROM SOME PORTION OR PORTIONS OF THE REMAINING 'UNOBSERVED' SEQUENCE ABOVE, BUT SINCE THE REGISTER WAS UNKNOWN, THE AUTHORS MODELLED IT AS A POLYALANINE STRAND, LISTED IN THE SEQRES AND COORDINATES AS UNK, UNKNOWN RESIDUE.