Secretory immunoglobulin (Ig) A is a decameric Ig composed of four α-heavy chains, four light chains, a joining (J) chain, and a secretory component (SC). The heavy and light chains form two tetrameric Ig molecules that are joined by the J chain and associate with the SC. Expression of a secretory monoclonaI antibody in tobacco (Nicotiana tabacum) has been described: this molecule (secretory IgA/G [SIgA/G]) was modified by having a hybrid heavy chain sequence consisting of IgG γ-chain domains linked to constant region domains of an IgA α-chain. In tobacco, about 70% of the protein assembles to its final, decameric structure. We show here that SIgA/G assembly and secretion are slow, with only approximately 10% of the newly synthesized molecules being secreted after 24 h and the bulk probably remaining in the endoplasmic reticulum. In addition, a proportion of SIgA/G is delivered to the vacuole as at least partially assembled molecules by a process that is blocked by the membrane traffic inhibitor brefeldin A. Neither the SC nor the J chain are responsible for Vacuolar delivery, because IgA/G tetramers have the same fate. The parent IgG tetrameric molecule, containing wild-type γ-heavy chains, is instead secreted rapidly and efficiently. This strongly suggests that intracellular retention and vacuolar delivery of IgA/G is due to the α-domains present in the hybrid α/γ-heavy chains and indicates that the plant secretory system may partially deliver to the vacuole recombinant proteins expected to be secreted.
CITATION STYLE
Frigerio, L., Vine, N. D., Pedrazzini, E., Hein, M. B., Wang, F., Ma, J. K. C., & Vitale, A. (2000). Assembly, secretion, and vacuolar delivery of a hybrid immunoglobulin in plants. Plant Physiology, 123(4), 1483–1493. https://doi.org/10.1104/pp.123.4.1483
Mendeley helps you to discover research relevant for your work.