Auxin binding protein is located in the lumen of the endoplasmic reticulum (ER). The primary structure contains an N-terminal hydrophobic leader sequence of 30-40 amino acids, which could represent a signal for translocation of the protein to the ER [<cite idref="PUB00001170"/>, <cite idref="PUB00004518"/>]. The mature protein comprises around 165 residues, and contains a number of potential N-glycosylation sites. In vitro transport studies have demonstrated co-translational glycosylation [<cite idref="PUB00004518"/>]. Retention within the lumen of the ER correlates withan additional signal located at the C terminus, represented by the sequence Lys-Asp-Glu-Leu, known to be responsible for preventing secretion of proteins from the lumen of the ER in eukaryotic cells [<cite idref="PUB00001170"/>, <cite idref="PUB00004518"/>].