cDNA clones of the auxin-binding protein from corn coleoptiles (Zea mays L.): isolation and characterization by immunological methods.

Abstract

An auxin‐binding protein (ABP) cDNA clone was selected from a lambda gt11 cDNA library from corn coleoptiles with highly purified IgGanti ABP. The sequence of 794 bp contains an open reading frame (ORF) of 603 bp, coding for a 22 kd protein. There are indications of a signal peptide of 38 amino acids (von Heijne, G. 1983, Eur. J. Biochem., 133, 17‐21). A N‐glycosylation site can be deduced and a C‐terminal KDEL amino acid sequence is detected. An EcoRI fragment containing the beginning portion of the cDNA with about three quarters of the ORF was used to select cDNA clones from an independently produced lambda gt11 cDNA library of corn coleoptiles. Northern blot analysis with in vitro transcribed biotinylated RNA showed a single band of not more than 850 bases. The full‐length in vitro transcript directed the in vitro synthesis of a protein which is precipitated by IgGanti ABP. Rabbit antibodies raised against a fusion protein detect the ABP as a double band on Western blots. Only the smaller of the two ABP bands is labeled by two different KDEL‐specific IgG preparations.

Perception of the auxin signal at the plasma membrane of tobacco mesophyll protoplasts

“…Answering this question will need further extensive molecular and biochemical analysis. As the sequence analysis of ABPl reveals no hydrophobic stretch large enough to constitute a transmembrane domain (Hesse eta/., 1989;lnohara eta/., 1989;Tillmann et a/., 1989), we assume that ABPl could interact with a transmembrane protein of tobacco plasma membrane (TP) essential for transmission of the auxin signal ( Figure 7a). Considering such a model, an auxin perception unit could b e formed by the association of a tARP with a TP (Figure 7al).…”

“…Several cDNA clones corresponding to this auxin binding protein have recently been isolated. The primary amino acid sequence deduced from these cDNAs defines a protein with an N-terminal hydrophobic leader sequence and a C-terminal signal consisting of the amino acids lysasp-glu-leu (KDEL), indicating that this major auxin binding protein in maize, ABP1, is a luminal component of the endoplasmic reticulum lnohara et al, 1989;Tillmann et a/., 1989). In addition, two proteins (ABP2 of 23 kDa and ABP3 of 22 kDa) antigenically related to ABPl , but present in very low amounts (less than 5% of the amount of ABPl), could be detected in maize coleoptiles using polyclonal antisera against ABPl .…”

The tobacco luminal binding protein is encoded by a multigene family.

“…The presence of a variable region in front of the HDEL peptide in tobacco BiP supports the view that the targeting information only resides in the last 4 amino acids. However, the putative auxin receptor located in the ER lumen of maize (Hesse et al, 1989;lnohara et al, 1989;Tillman et al, 1989) and the luminal enzyme sulfhydryl endopeptidase of Vigna mungo (Akasofu et al, 1989) both contain the mammalian signal (KDEL) for reticuloplasmin retention. This suggests either that different retention signals are used between different plant species or that both signals are functional in plants.…”

AUXIN BINDING PROTEIN1: The Outsider

“…The biochemical properties of this binding activity were characterized Ray, 1977;Venis, 1977), but it was not until 1985 that Zm-ABP1 protein was purified (Lö bler and Klä mbt, 1985) and subsequently molecularly cloned Inohara et al, 1989;Tillmann et al, 1989). In the same year, it was also proven that ABP1 indeed binds auxin (Jones and Venis, 1989), a result that was later corroborated by the crystal structure determination of ABP1 cocrystallized with auxin (Woo et al 2002).…”

“…The canonical ABP1 of flowering plants contains an N-terminal signal peptide for entry into the secretory pathway and a C-terminal endoplasmic reticulum (ER) retention sequence of the KDEL type (Lys-Asp-Glu-Leu) Inohara et al, 1989;Tillmann et al, 1989). Other, less common types of ER retention signals exist in ABP1 of ferns and gymnosperms (Tromas et al, 2010), whereas ABP1 orthologs from several moss species do not contain a known ER retention motif (Panigrahi et al, 2009), and not all clades of green algae have bona fide ABP1 orthologs (Tromas et al, 2010).…”