Structural characterization of reverse transcriptase and endonuclease polypeptides of the acquired immunodeficiency syndrome retrovirus.

Automated N-terminal microsequencing of immune affinity-purified acquired immunodeficiency syndrome retrovirus polypeptides from infected cells was used to locate the N termini of 64-, 51-, and 34-kilodalton (kDa) polypeptides within the pol open reading frame (ORF) of the proviral DNA. The 64- and 51-kDa proteins had identical N termini (Pro-Ile-Ser-Pro-IIe-Glu-Thr-Val-) positioned 156 residues from the beginning of the pol ORF. The N terminus of the 34-kDa pol gene product, Phe-Leu-Asp-Gly-Ile-Asp-Lys-, mapped 716 residues into the pol ORF. These polypeptides were absent in an RT-negative, CD4-negative, persistently infected cell line (8E5) carrying a single defective copy of a constitutively expressed, integrated proviral DNA.