title: Cotranslational amino-terminal processing of cytosolic proteins. Cell-free expression of site-directed mutants of human hemoglobin.
abstract: The diversity of protein structure is significantly enhanced by cotranslational and posttranslational modifications. Structural features at the amino terminus are especially important contributors to protein function and stability. Amino-terminal processing of cytosolic proteins includes the cleavage of the initiator methionine and N alpha-acetylation. To better understand the rules that govern these cotranslational events, site-directed mutants of the human beta-globin gene encoding for all 19 amino acid replacements of Val-beta 1 were expressed in a cell-free transcription and translation system. The initiator methionine was 100% cleaved when the side chain of the adjacent residue was relatively small (radius of gyration less than 1.29 A), whereas the initiator methionine was 100% retained when the side chain was relatively large. The extent of N alpha-acetylation ranged from 0 to 100% depending on the amino-terminal sequence. The experimental results in this cell-free system faithfully mimic what occurs in nature as judged by the structures of normal and variant human hemoglobins as well as a broad spectrum of other cytosolic proteins.
authors: Laboratory of the Howard Hughes Medical Institute, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115.
authors: J P
authors: JP
authors: Boissel
authors: T J
authors: TJ
authors: Kasper
authors: H F
authors: HF
authors: Bunn
mesh_terms: D000596:Amino Acids / Q000032:analysis; D002474:Cell-Free System; D006454:Hemoglobins / Q000096:biosynthesis / Q000235:genetics*; D006801:Humans; D007525:Isoelectric Focusing; D014176:Protein Biosynthesis
chemical_list: D000596:Amino Acids; D006454:Hemoglobins