The C-terminal sequence from common bugle leaf galactan:galactan galactosyltransferase is a non-sequence-specific vacuolar sorting determinant.
The Ajuga reptans L. galactan:galactan galactosyltransferase (ArGGT) is a vacuolar enzyme that synthesizes long-chain raffinose family oligosaccharides (RFOs), the major storage carbohydrates of this plant. ArGGT is structurally and functionally related to acid plant alpha-galactosidases (alpha-Gals) of the glycosylhydrolase family 27, present in the apoplast or the vacuole. Sequence comparison of acid alpha-Gals with ArGGT revealed that they all contain an N-terminal signal sequence and a highly similar core sequence. Additionally, ArGGT and some acid alpha-Gals contain C-terminal extensions with low sequence similarities to each other. Here, we show that the C-terminal pentapeptide, SLQMS, is a non-sequence-specific vacuolar sorting determinant. Analogously, we demonstrate that the C-terminal extensions of selected acid alpha-Gals from Arabidopsis, barley, and rice, are also non-sequence-specific vacuolar sorting determinants, suggesting the presence of at least one vacuolar form of acid alpha-Gal in every plant species.
Tapernoux-Lüthi
Esther M
EM
Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, CH-8008 Zurich, Switzerland.
Schneider
Thomas
T
Keller
Felix
F
D031328:Ajuga / Q000201:enzymology; D000595:Amino Acid Sequence; D005700:Galactosyltransferases / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport; D017386:Sequence Homology, Amino Acid; D014617:Vacuoles / Q000378:metabolism*
D021382:Protein Sorting Signals; D005700:Galactosyltransferases; C488493:galactan-galactan galactosyltransferase, Ajuga reptans