Primary Structure of κ Light Chain from a Human Myeloma Protein.

The primary structure of the light chain of myeloma protein Car was studied. The light chain was fully reduced and alkylated with iodo[¹⁴C]acetic acid and digested with trypsin. The tryptic peptides were purified and sequenced. Peptides that overlapped the tryptic peptides were isolated from a peptic digest. The object was primarily to sequence the variable part of the chain, whereas the peptides of the constant part were only partially sequenced. The amino acid sequence of the variable part coincides with the basic sequence of the κIb subgroup, except for few substitutions. Some of the above-mentioned substitutions are unique and some have been observed already in other κI chains. Two unusual features of this light chain are the presence of carbohydrate covalently bound to the asparagine residue occupying position 28 and the deletion of one amino acid at position 95. [ABSTRACT FROM AUTHOR]