Title : O-linked glycosylation of rat renal
gamma-glutamyltranspeptidase adjacent to its membrane anchor
domain
Abstract :
- Large domains rich in serine and threonine , that are likely to exhibit clusters of O-linked oligosaccharides, have been reported adjacent to the anchor of several cell surface proteins
- No such domain is evident in the primary sequence of rat renal gamma-glutamyltranspeptidase
- However, papain treatment of the amphipathic enzyme ( Triton-purified gamma-glutamyltranspeptidase , T gamma GT), pretreated with galactose oxidase and NaB3H4 (Frielle, T., and Curthoys, N. P. (1983) Biochemistry 22, 5709-5714), yields the hydrophilic enzyme (papain-treated Triton-purified gamma-glutamyltranspeptidase , PT gamma GT) and a labeled peptide which contains both the amino-terminal membrane anchor and the sequence Pro27-Thr28-Thr29-Ser30
- Since [3H]galactose was identified in this peptide, the presence of O-linked oligosaccharides was investigated
- Carbohydrate analysis is consistent with the presence of two simple O-linked oligosaccharides on T gamma GT and one on PT gamma GT
- Lectin blot analysis of T gamma GT and PT gamma GT was carried out after sodium dodecyl sulfate-polyacrylamide gel electrophoresis
- The small subunits of both T gamma GT and PT gamma GT and the large amphipathic subunit of T gamma GT all react with the peanut agglutinin lectin , but the large subunit of PT gamma GT exhibits no such reactivity
- The reactivity with PNA is consistent with the presence of one oligosaccharide with the structure galactose beta 1-3N-acetylgalactosamine alpha 1-Ser/Thr attached to each subunit of T gamma GT
- The papain-sensitivity of the oligosaccharide from the larger subunit is consistent with O-glycosylation at the Thr28-Thr29-Ser30 sequence
- The results of lectin blot analysis with wheat germ agglutinin imply that the content of N-linked oligosaccharides is unaffected by papain treatment of the transpeptidase
- These data represent the first direct evidence for O-glycosylation of a microvillar hydrolase at a site immediately adjacent to the membrane anchor and indicates that even small clusters of Thr and Ser can be O-glycosylated
- Isolated O-linked oligosaccharides may have functional significance since single Ser and Thr residues are consistently found near the membrane anchor of many cell surface proteins
Output (sent_index, trigger,
protein,
sugar,
site):
- 0. glycosylation, , gamma-glutamyltranspeptidase, -, -
- 11. O-glycosylated, , -, even small clusters, -
- 11. O-glycosylation, , hydrolase, -, -
- 11. Ser, , -, even small clusters, Thr and Ser
- 11. Thr, , -, even small clusters, Thr and Ser
- 9. O-glycosylation, , -, -, sequence
Output(Part-Of) (sent_index,
protein,
site):
- 1. Large, domains
- 2. gamma-glutamyltranspeptidase, sequence
*Output_Site_Fusion* (sent_index,
protein,
sugar,
site):