An amino-terminal amino acid affects the electrophoretic mobility of the HIV-1 nef protein.
The nef protein of the BH8 clone derived from the IIIB isolate of human immunodeficiency virus 1 (HIV-1) has a molecular weight of 27,000, whereas that produced by a clone of the BRU strain of HIV-1 appears to have a molecular weight of 24,800. To determine the basis for this difference in molecular weight, a series of recombinant nef genes were made in which segments of the BH8 and BRU nef coding sequences were exchanged. The region of amino acids 35-74 caused mobility shift. In this region, the BH8 and BRU proteins differ by a single amino acid at position 54. Residue 54 of BH8 nef is an aspartic acid, whereas that of BRU is alanine. Reciprocal changes in the sequences of BH8 and BRU nef were made by site-directed mutagenesis. The results show that substitution of aspartic acid at residue 54 of BH8 to alanine results in a protein that has a molecular weight of 25,000, and substitution of the alanine at position 54 of BRU to aspartic acid results in synthesis of a 27-kDa protein. These results show that a change in amino acid 54 of the HIV-1 nef protein dramatically affects the electrophoretic mobility of the protein. Nef proteins that contain an aspartic acid at residue 54 migrate as 27-kDa proteins, whereas those that contain alanine at residue 54 migrate as 25-kDa proteins.
Obaru
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Division of Human Retrovirology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts.
DeClue
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Haseltine
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D000409:Alanine / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry*; D004586:Electrophoresis; D015693:Gene Products, nef / Q000737:chemistry*; D015497:HIV-1 / Q000737:chemistry*; D008970:Molecular Weight; D011487:Protein Conformation; D054311:nef Gene Products, Human Immunodeficiency Virus
D015693:Gene Products, nef; D054311:nef Gene Products, Human Immunodeficiency Virus; D001224:Aspartic Acid; D000409:Alanine