Independent expression of the gene coding for the constant domain of immunoglobulin light chain: Evidence from sequence analyses of the precursor of the constant region polypeptide

Abstract

The mRNA coding for the K-type constant region (C,,) was purified from two clones derived from the MPC-1I mouse myeloma. This mRNA directs the cell-free synthesis of a C, precursor (molecular weight, about 15,000) in which an extra piece, 17 residues long, precedes the NH1ter-minal residue (Ma'19) of the C. region. Te partial sequence of the extra piece is: Met-X-Thr-Asp-Thr-Leu-Leu-Leu-Trp ValLeu-Leu-Leu-Trp-Val-Pro-X-(X is unknown). Met1 was shown to be the initiator methionine. The sequence of the C, extra piece is completely different from any known sequence preceding residue Ma'° § in whole light (L) (i) translocation of this V gene to the C gene, deletion of the entire mature V gene, and "end-toend" repair of the remaining xp-DNA to the C gene; (ii) translocation to the C gene only of the xp-DNA portion of the V gene.

Conformational studies of the synthetic precursor-specific region of preproparathyroid hormone.

“…In general, higher peptide concentrations promote 1-sheet conformation; however, in this case, the peptide concentration in aqueous buffer was less than that in the nonpolar solvent. DISCUSSION NH2-terminal extensions are a common structural feature of nearly all precursor forms of secreted proteins (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). These NH2-terminal peptide segments may represent specialized sequences that serve an essential function in facilitating intracellular transport and processing of secreted proteins (16)(17)(18)(19)(20).…”

“…Parathyroid hormone (PTH), like other secreted proteins (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14), is initially biosynthesized in a larger precursor form, preproparathyroid hormone (preproPTH), which contains an NH2-terminal extension, or leader sequence (15). Although the biological role of precursor regions in the biosynthesis, posttranslational modification, and intracellular transport of secreted proteins remains to be fully elucidated, it is thought that leader sequences promote the initial steps in protein secretion: the interaction of nascent peptide chains with intracellular membranes and the subsequent entry of protein into the cisternae of the rough endoplasmic reticulum (RER) (16)(17)(18)(19)(20).…”

Initiation and processing in vitro of the primary translation products of guinea-pig caseins

“…Mellor, unpublished work). Our observation that the unformylated initiating methionine was not removed from the nascent polypeptide chain was not unexpected, as sequencing studies of many different proteins have shown that in vitro the initiating N-terminal methionine is retained (Burstein et al, 1977;Palmiter et al, 1978b;Mellor & Smith, 1978). Our experiments with a membrane-supplemented cell-free system, using [31S]methionyl-tRNAM't or the free amino acid, demonstrate that the addition of microsomal membranes results in the processing of all the milk-protein primary translation products.…”

Germ line transcription of the immunoglobulin heavy chain locus directs production of mu chain without VDJ.

“…The truncated g chains, both LS-CM and DQ, may combine with the light chain surrogates lambdaS and Vpre-B to form a pseudo-immunoglobulin molecule without variable region (34,35). Polypeptides with sequence predicted by the K0 nucleic acid sequence have been reported (36,37). The DB transcripts ofT cell antigen receptor have an upstream ATG initiation codon with following open reading frame with the properties of a leader sequence, suggesting that this intermediate may be translated as well (26).…”