Selective processing of proalbumin determined by site-specific mutagenesis.
Rat proalbumin is cleaved at the dibasic pair Arg-Arg and converted into a mature form with Glu at the NH2 terminus. In the present study site-directed mutagenesis of the albumin cDNA was designed to generate proalbumin variants in which Glu1 was substituted with various amino acid residues. The expression plasmids constructed were transfected into COS-1 cells, and the intracellular processing of proalbumins expressed was examined by labeling experiments. Substitution of Glu1----Ser allowed the expressed proalbumin to be processed as observed for the wild-type precursor. However, replacement of Glu1 with a hydrophobic residue (Val, Leu or Ile) resulted in no processing of proalbumin, despite retaining the same cleavage signal Arg-Arg as above. The results indicate that the residue at position 1 adjacent to the dibasic pair is also important for recognition by the proalbumin-processing enzyme.
Oda
K
K
Department of Biochemistry, Fukuoka University School of Medicine, Japan.
Misumi
Y
Y
Sohda
M
M
Takami
N
N
Sakaki
Y
Y
Ikehara
Y
Y
D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D004252:DNA Mutational Analysis; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D011228:Prealbumin / Q000235:genetics / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D051381:Rats; D013329:Structure-Activity Relationship; D014162:Transfection
D011228:Prealbumin; D011498:Protein Precursors