A single amino acid substitution in a common African allele of the CD4 molecule ablates binding of the monoclonal antibody, OKT4.
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Lederman S, DeMartino JA, Daugherty BL, Foeldvari I, Yellin MJ, Cleary AM, Berkowitz N, Lowy I, Braunstein NS, Mark GE, et al.
A single amino acid substitution in a common African allele of the CD4 molecule ablates binding of the monoclonal antibody, OKT4.
Mol Immunol. 1991 Nov;28(11):1171-81.
- PubMed ID
- 1961196 [ View in PubMed]
- Abstract
The CD4 molecule is a relatively non-polymorphic 55 kDa glycoprotein expressed on a subset of T lymphocytes. A common African allele of CD4 has been identified by non-reactivity with the monoclonal antibody, OKT4. The genetic basis for the OKT4- polymorphism of CD4 is unknown. In the present paper, the structure of the CD4 molecule from an homozygous CD4OKT4- individual was characterized at the molecular level. The size of the CD4OKT4- protein and mRNA were indistinguishable from those of the OKT4+ allele. The polymerase chain reaction (PCR) was used to map the structure of CD4OKT4- cDNAs by amplifying overlapping DNA segments and to obtain partial nucleotide sequence after asymmetric amplification. PCR was then used to clone CD4OKT4- cDNAs spanning the coding region of the entire, mature CD4 protein by amplification of two overlapping segments followed by PCR recombination. The nucleotide sequence of CD4OKT4- cDNA clones revealed a G----A transition at bp 867 encoding an arginine----tryptophan substitution at amino acid 240 relative to CD4OKT4+. Expression of a CD4OKT4- cDNA containing only this transition, confirmed that the arginine----tryptophan substitution at amino acid 240 ablates the binding of the mAb OKT4. A positively charged amino acid residue at this position is found in chimpanzee, rhesus macaque, mouse and rat CD4 suggesting that this mutation may confer unique functional properties to the CD4OKT4- protein.