J. Biol. Chem., Vol. 265, Issue 15, 8420-8425, 05, 1990
The functional efficiency of a mammalian signal peptide is directly related to its hydrophobicity
P Bird, MJ Gething and J Sambrook
Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas 75235.
We have previously shown that the signal sequence of the Saccharomyces
cerevisiae vacuolar protein carboxypeptidase Y (CPY) does not function in
mammalian cells unless a glycine residue in the central core is replaced by
leucine. Additional mutants were constructed to investigate the features of
this hydrophobic core (h) region that are important for signal sequence
function in mammalian cells. We find that the degree of hydrophobicity of
the h region of any particular mutant signal is directly related to the
efficiency with which it directs the translocation of CPY. A minimal h
region in a functional signal appears to consist of five hydrophobic
residues interrupted by 1 glycine. Analysis of potential secondary
structures suggests that a functional mutant signal is more likely than the
nonfunctional CPY signal to adopt either a beta strand or an alpha-helical
conformation.