Fig. 6. Reconstitution of efficient transport by a minimal number of transport determinants in a signal-less reporter. (A) GM construct and signal-less GM constructs reconstituted with a minimal set of anterograde transport determinants. The signal-less constructs possess a polyleucine TMD and a poly-alanine or poly-serine cytoplasmic domain. The minimal anterograde transport determinants are in bold. All constructs were prepared without and with alanine substitution of cysteine 466 alone, or cysteine 466 together with cysteine 475. (B) Oligomerization of reconstituted constructs. The reconstituted constructs with alanine (ala tail) or serine tail (ser tail) were tested for disulfide-linked oligomerization as described in Fig. 2, except that only one time point was analyzed (15 min chase). 1x, cysteines 466 and 475 have been substituted; 2x, cysteine 466 has been substituted; 6x, both cysteines are present. (C,D) Transport of GM constructs expressed in COS cells probed by pulse-chase/endo H (Fig. 1). rec, reconstituted constructs with cysteine substitutions indicated; sl, signal-less constructs. The `sl' and `rec' constructs contain alanine tails in panel C, and serine tails in panel D. Mean±s.e.m. of at least three independent experiments.