In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 99, No. 1 ( 2002-01-08), p. 60-65
Abstract:
KAT1 is a member of the Shaker family of voltage-dependent
K + channels, which has six transmembrane segments (called
S1–S6), including an amphipathic S4 with several positively charged residues and a hydrophobic pore-forming region (called P) between S5
and S6. In this study, we systematically evaluated the function of individual and combined transmembrane segments of KAT1 to direct the
final topology in the endoplasmic reticulum membrane by in
vitro translation and translocation experiments. The assay with
single-transmembrane constructs showed that S1 possesses the type II signal-anchor function, whereas S2 has the stop-transfer function. The
properties fit well with the results derived from combined insertion of S1 and S2. S3 and S4 failed to integrate into the membrane by
themselves. The inserted glycosylation sequence at the S3–S4 loop neither prevented the translocation of S3 and S4 nor impaired the
function of voltage-dependent K + transport regardless of
the changed length of the S3–S4 loop. S3 and S4 are likely to be posttranslationally integrated into the membrane only when somewhat
specific interaction occurs between them. S5 had the ability of translocation reinitiation, and S6 had a strong preference for
N exo /C cyt orientation. The pore region
resided outside because of its lack of its transmembrane-spanning property. According to their own topogenic function, combined
constructs of S5–P–S6 conferred the membrane-pore-membrane topology. This finding supports the notion that a set of S5–P–S6 can be
independently integrated into the membrane. The results in this study provide the fundamental topogenesis mechanism of transmembrane segments
involving voltage sensor and pore region in KAT1.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.012399799
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2002
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12