Functions of signal and signal-anchor sequences are determined by the balance between the hydrophobic segment and the N-terminal charge.
The signal sequence of secretory proteins and the signal-anchor sequence of type II membrane proteins initiate the translocation of the following polypeptide segments, whereas the signal-anchor sequence of cytochrome P-450-type membrane proteins mediates the membrane insertion of the polypeptide via a signal-recognition particle-dependent mechanism but does not lead to the translocation of the following C-terminal sequences. To establish the structural requirements for the function of signal and signal-anchor sequences, we constructed chimeric proteins containing artificial topogenic sequences in which the N-terminal net charge and the length of the hydrophobic segment were systematically altered. Utilizing an in vitro translation-translocation system, we found that hydrophobic segments consisting of 7-10 leucine residues functioned as signal sequences whereas segments with 12-15 leucine residues showed different topogenic functions, behaving as signal sequences or P-450-type signal-anchor sequences, depending on the N-terminal charge. From these observations, we propose that the function of N-terminal topogenic sequences depends on a balance between the N-terminal charge and the length of the following hydrophobic segment.
Sakaguchi
M
M
Department of Molecular Biology, Graduate School of Medical Science, Fukuoka, Japan.
Tomiyoshi
R
R
Kuroiwa
T
T
Mihara
K
K
Omura
T
T
D001483:Base Sequence; D002451:Cell Compartmentation; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D021382:Protein Sorting Signals / Q000737:chemistry*; D011994:Recombinant Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship
D008565:Membrane Proteins; D009838:Oligodeoxyribonucleotides; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; D003577:Cytochrome P-450 Enzyme System