Sequence Studies on Bence Jones Proteins

One Bence Jones protein and two Bence Jones fragments (fragmentary chains) of K type, and one Bence Jones protein and two fragments of L type have been analyzed. These proteins have been aminoethylated and digested with proteolytic enzymes. The resulting peptides were separated by different procedures.The peptides obtained were analyzed and could be located in most cases in the amino acid sequence of the corresponding protein by homology with published sequences. These tentative sequences were particularly satisfactory in the case of the three K type proteins. These belonged to subtype KI and showed considerable homologies with other KI proteins. It was more difficult to position peptides of the three L type proteins on the basis of homology with published sequences. Several peptides of one protein (BJ 98) which were completely sequenced by Edman degradation combined with proteolytic digestion could not be positioned.Amino acid analysis of peptides obtained from Bence Jones fragments confirmed that these correspond to the N‐terminal varible region of Bence Jones proteins for K type fragments, whereas they extend for three residues over the C‐terminal constant region for some L type