Processing and trafficking of a single isoform of the aspartic proteinase cardosin A on the vacuolar pathway |
| |
Authors: | Patrícia Duarte José Pissarra Ian Moore |
| |
Institution: | (1) IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal;(2) Department of Plant Sciences, University of Oxford, South Parks Rd, Oxford, OX1 3RB, UK;(3) Department of Botany, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 1191, 4150-181 Porto, Portugal |
| |
Abstract: | Cardosin A is the major vacuolar aspartic proteinase (APs) (E.C.3.4.23) in pistils of Cynara
cardunculus L. (cardoon). Plant APs carry a unique domain, the plant-specific-insert (PSI), and a pro-segment which are separated from
the catalytic domains during maturation but the sequence and location of processing steps for cardosins have not been established.
Here transient expression in tobacco and inducible expression in Arabidopsis indicate that processing of cardosin A is conserved in heterologous species. Pulse chase analysis in tobacco protoplasts
indicated that cleavage at the carboxy-terminus of the PSI could generate a short-lived 50 kDa intermediate which was converted
to a more stable 35 kDa intermediate by removal of the PSI. Processing intermediates detected immunologically in tobacco leaves
and Arabidopsis seedlings confirmed that cleavage at the amino-terminus of the PSI either preceded or followed quickly after cleavage at
its carboxy-terminus. Thus removal of PSI preceded the loss of the prosegment in contrast to the well-characterised barley
AP, phytepsin. PreprocardosinA acquired a complex glycan and its processing was inhibited by brefeldin A and dominant-inhibitory
AtSAR1 or AtRAB-D2a mutants indicating that it was transported via the Golgi and that processing followed ER export. The 35 kDa intermediate was
present in the cell wall and protoplast culture medium as well as the vacuole but the 31 kDa mature subunit, lacking the amino-terminal
prosegment, was detected only in the vacuole. Thus maturation appears to occur only after sorting from the trans-Golgi to
the vacuole. Processing or transport of cardosin A was apparently slower in tobacco protoplasts than in whole cells.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
| |
Keywords: | Arabidopsis Dexamethasone Nicotiana Phytepsin pOp6 LhGR Rab1 |
本文献已被 PubMed SpringerLink 等数据库收录! |
|