Membrane topogenesis of a type I signal-anchor protein, mouse synaptotagmin II, on the endoplasmic reticulum

Yuichiro Kida, Masao Sakaguchi, Mitsunori Fukuda, Katsuhiko Mikoshiba, Katsuyoshi Mihara

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)


Synaptotagmin II is a type I signal-anchor protein, in which the NH2-terminal domain of 60 residues (N-domain) is located within the lumenal space of the membrane and the following hydrophobic region (H-region) shows transmembrane topology. We explored the early steps of cotranslational integration of this molecule on the endoplasmic reticulum membrane and demonstrated the following: (a) The translocation of the N-domain occurs immediately after the H-region and the successive positively charged residues emerge from the ribosome. (b) Positively charged residues that follow the H-region are essential for maintaining the correct topology. (c) It is possible to dissect the lengths of the nascent polypeptide chains which are required for ER targeting of the ribosome and for translocation of the N-domain, thereby demonstrating that different nascent polypeptide chain lengths are required for membrane targeting and N-domain translocation. (d) The H-region is sufficiently long for membrane integration. (e) Proline residues preceding H-region are critical for N-domain translocation, but not for ER targeting. The proline can be replaced with amino acid with low helical propensity.

Original languageEnglish
Pages (from-to)719-729
Number of pages11
JournalJournal of Cell Biology
Issue number4
Publication statusPublished - 2000 Aug 21


  • Membrane protein
  • Membrane topology
  • Protein translocation
  • Signal-anchor sequence
  • Translocon


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