During the development of B cells there is switch from the synthesis of membrane-bound immunoglobulin to a secreted form of immunoglobulin. This change occurs because the mRNA population encodes a protein missing which of the following sequence motifs?

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Quizplus · Accepted Answer

The switch from membrane-bound to secreted immunoglobulin involves the absence of the anchor sequence in the mRNA, which is necessary for membrane attachment.  Membrane-bound and secreted proteins are synthesized by ribosomes attached to the membranes of the ER. As synthesis of these types of proteins begins a complex on the ER called the signal recognition particle (SRP) engages the signal peptide of the newly synthesizing protein. The SRP then assists in the transfer of the elongating peptide through the ER membrane into the lumen of the ER. Proteins that are membrane bound contain a stretch of hydrophobic amino acids that constitutes the transmembrane domain(s). These hydrophobic amino acids stop the transfer of the protein into the ER lumen and are referred to as anchor sequences or stop-transfer sequences.

During the Development of B Cells There Is Switch from the Synthesis