standar

l«i

Positive

domain

I lydrophobic domain

Cleavage recogniiion zonę

i Rest of | protein

(;k n■i u

Qnmige sile

FIGURĘ 8.26

Standard Signal Seguence for Exported Proteins

The signal sequence conłains a posiłive charged domain Icontaining łysinę and/or arginine), an a* helical hydrophobic domain (rich in alaninę, leucine and valine) and a cleavage sito preceded by a glycine or serine and followed by a proline. A reverse lurn due to glycine is found appfoximately half way through łhe hydrophobic domain.

FIGURĘ 8.27 Cotranslational Export of Proteins

A) The ribosome making the polypeplide choin approaches łhe celi membranę. The polypephde wiłh ih signal scqucncc binds k> łhe signal recogniiion protein B) The signal recogniiion protein recognizes the translocase and binds k> il, allowing łhe polypeplide chain lo begin ils joumey łhrough łhe mcm bronę. Cl After łhe signal sequence exils łhe tronslocase, leoder peplidase culs łhe polypeplide chain, liberaling łhe signal peptide. D) Finał (olding of łhe protein occurs oulside the celi.