Purification of the CFTR protein from transiently expressed HEK
cells. Silver staining of aliquots at each purification step from
anti-FLAG (a) and from WGA columns (b). Proteins bound to
the WGA column were eluted by a linear gradient of GlcNAc from 20 to 100
mm. Bands of fully glycosylated mature CFTR are indicated by
arrowheads. c, CFTR-rich eluates from the WGA column were
concentrated using the Microcon YM-100 filter unit and analyzed by Superdex
200 SEC. CFTR was eluted in a sharp peak at 1.04-ml elution (indicated by an
arrow). d, SDS-PAGE analysis of the SEC fractions. The
intensity of the CFTR band in the gel corresponds to absorption in SEC. The
fraction at 1.04 ml (arrow) was used for EM image analysis.
e, from the elution volumes of CFTR and the standards, the
RS of CFTR was calculated as 74.8 ± 1.1 Å
(mean ± S.D., n = 5). T, thyroglobulin
(RS, 85.0 Å); F, ferritin
(RS, 61.0 Å); C, catalase
(RS, 52.2 Å); A, aldolase
(RS, 48.1 Å).