The molecular cloning and nucleotide sequence of the cDNA for human Cu/Zn superoxide dismutase (SOD) is reported. The tacI promoter has been used to direct the synthesis in E. coli of this SOD which is soluble, stable, and of normal specific activity. The N-terminal methionine is removed from this protein. A construction with a ribosome binding site identical to that of the lacz gene 5' of the initiator methionine codon, resulted in low levels of SOD. An in vitro mutagenesis procedure was used to randomise the four nucleotides preceding the initiator methionine codon and the silent third positions of the codons specifying the second and third amino acids. Analysis of a sample of 500 clones showed that ca. 25 clones synthesised 5% or more of soluble cell protein as SOD. The nucleotide sequences of high level expressors showed a predominance of A and T residues in t e variable positions 5' of the initiator methionine codon. An SOD mutant (ala +gln) was discovered during the sequencing and shown to lack dismutation activity. Secondary structure predictions for the 5' regions of the mRNAs from high and low level expressors support the hypothesis that initiation of translation is much reduced if part of the region complementary to 16s rRNA is base paired in a stem structure.

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MethodsTwo T helper cell clones recognizing the gp 120 envelope protein of HIV were generated from the peripheral blood of a healthy seropositive individual. These cells were type specific as they proliferated and produced IL 2 when stimulated by an epitope in the amino-terminal half of gp 120 of HIVsF2, but not by a similar region of HIVz,6, a Zairian HIV-1 isolate. These two viruses differ by 26% in the deduced amino sequence of the gp 120 protein. Moreover, the antigenic site(s) recognized by the cloned T cells are distinct from those recognized by envelope-specific antibodies. These observations have important implications for the development and use of anti-HIV vaccines.

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