Constructs used to express recombinant gp41 in the E. coli system. (A) The expression vectors used in this study. The env gene is derived from HIV-1 HXB2 strain. gp41 starts amino acid 636 and ends with the various C-terminal positions as indicated in Fig. 1A. The schema below the plasmid map shows the components of the recombinant proteins. The truncated gp41 is preceded by maltose binding protein (MBP) and followed by the topological reporter, green fluorescent protein (GFP). The nomenclatures are as follows: lacI, lacI repressor gene; pTac, a hybrid promoter between trp and lac promoters; CT, cytoplasmic tail; AmpR, ampicilin resistant gene; f1ori, replication origin of f1; pER322ori, replication origin of pBR322 plasmid. (B) Expression of the recombinant proteins. The immunoblotting of bacterial lysates probed with the anti-GFP antibody is shown. The name on the top of each lane indicates the expression vector used (see Table 1).