Linked Life Data

11865036

Source:http://linkedlifedata.com/resource/pubmed/id/11865036

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
Pt 4
pubmed:dateCreated
2002-2-26
pubmed:abstractText
The variant surface glycoproteins (VSG) of Trypanosoma brucei are anchored to the cell surface via a glycosylphosphatidylinositol (GPI) anchor. All GPI-anchored proteins are synthesized with a C-terminal signal sequence, which is replaced by a GPI-anchor in a rapid post-translational transamidation reaction. VSG GPI signal sequences are extraordinarily conserved. They contain either 23 or 17 amino acids, a difference that distinguishes the two major VSG classes, and consist of a spacer sequence followed by a more hydrophobic region. The omega amino acid, to which GPI is transferred, is either Ser, Asp or Asn, the omega+2 amino acid is always Ser, and the omega+7 amino acid is almost always Lys. In order to determine whether this high conservation is necessary for GPI anchoring, we introduced several mutations into the signal peptide. Surprisingly, changing the most conserved amino acids, at positions omega+1, omega+2 and omega+7, had no detectable effect on the efficiency of GPI-anchoring or on protein abundance. Several more extensive changes also had no discernable impact on GPI-anchoring. Deleting the entire 23 amino-acid signal sequence or the 15 amino-acid hydrophobic region generated proteins that were not anchored. Instead of being secreted, these truncated proteins accumulated in the endoplasmic reticulum prior to lysosomal degradation. Replacing the GPI signal sequence with a proven cell-surface membrane-spanning domain reduced expression by about 99% and resulted not in cell surface expression but in accumulation close to the flagellar pocket and in non-lysosomal compartments. These results indicate that the high conservation of the VSG GPI signal sequence is not necessary for efficient expression and GPI attachment. Instead, the GPI anchor is essential for surface expression of VSG. However, because the VSG is a major virulence factor, it is possible that small changes in the efficiency of GPI anchoring, undetectable in our experiments, might have influenced the evolution of VSG GPI signal sequences.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0021-9533
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
115
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
805-16
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2002
pubmed:articleTitle
Mutational analysis of the variant surface glycoprotein GPI-anchor signal sequence in Trypanosoma brucei.
pubmed:affiliation
Laboratory of Molecular Parasitology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't