M. Horiuchi et al., Surface-localized glycine transporters 1 and 2 function as monomeric proteins in Xenopus oocytes, P NAS US, 98(4), 2001, pp. 1448-1453
Citations number
38
Categorie Soggetti
Multidisciplinary
Journal title
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Na+/Cl--dependent neurotransmitter transporters form a superfamily of trans
membrane proteins that share 12 membrane-spanning regions. To gain informat
ion about the quaternary structure of these transporter proteins, we hetero
logously expressed the glial glycine transporter GlyT1 and its neuronal hom
olog GlyT2 in Xenopus oocytes. By using metabolic labeling with [S-35]methi
onine or surface labeling with a plasma membrane impermeable reagent follow
ed by affinity purification, we separately analyzed the total cellular pool
s of newly synthesized GlyTs and its functional plasma membrane-bound fract
ions. Upon blue native gel electrophoresis, the surface-localized transport
er proteins were found to exist exclusively in complex-glycosylated monomer
ic form, whereas a significant fraction of the intracellular GlyT1 and GlyT
2 was core-glycosylated and oligomeric. In contrast, even after treatment w
ith the crosslinker glutaraldehyde, surface GlyTs failed to migrate as olig
omeric proteins. These results indicate that plasma membrane-bound GlyT1 an
d GlyT2 are monomeric proteins, Thus, Na+/Cl--dependent neurotransmitter tr
ansporters do not require oligomerization for substrate translocation.