JBC, Vol. 250, Issue 1, 171-174, Jan, 1975
Initiation by methionine of mouse immunoglobulin light chain containing NH-2terminal pyroglutamic acid
C. Prasad and A. Peterkofsky
The mechanism of biosynthesis of NH2-terminal pyroglutamic acid has been
studied in a mouse plasmacytoma (RPC-20) which produces an immunoglobulin
light (lambda) chain containing NH2-terminal pyroglutamic acid. To this
end, initation of lambda chain synthesis in plasmacytoma cell suspensions
has been investigated. The analysis of radioactive lambda chain synthesis
by these cells was accomplished with an antibody preparation specific for
the precipitation of lambda chain protein from total plasmacytoma protein.
NH2-terminal analysis of plasmacytoma cells labeled with [35S]methionine
showed that the ratio of radioactivity in NH2-terminal methionine to total
incorporation in lambda chain was greater at 2 min of labeling than at 60
min. However, such a pattern of transient labeling of the NH2 terminus of
the lambda chain was not obtained when cells were incubated with tritiated
leucine, arginine, or tryptophan. The data indicate that methionine is the
initiator amino acid for the synthesis of lambda chain containing
NH2-terminal pyroglutamic acid.