Which is the most typical peptide sequence responsible for retrieval of endoplasmic reticulum (ER) lumenal proteins from the Golgi apparatus?
['Retention of soluble proteins in the endoplasmic reticulum is dependent on their interaction with the KDEL (Lys-Asp-Glu-Leu) receptor in the Golgi apparatus and their subsequent retrieval back to the endoplasmic reticulum.', 'the retrieval system for lumenal ER proteins. These proteins carry a specific sorting signal, typically the tetrapeptide KDEL, which is bound by a receptor in the Golgi apparatus.', 'The carboxyl-terminal Lys-Asp-Glu-Leu (KDEL), or a closely-related sequence, is important for ER localization of both lumenal as well as type II membrane proteins. This sequence functions as a retrieval signal at post-ER compartment(s)', 'the KDEL receptor is concentrated in the intermediate compartment, as well as in the Golgi stack', 'retrieval of KDEL-containing proteins occurs at multiple post-ER compartments up to the TGN along the exocytotic pathway', 'The erd2 protein is the receptor responsible for recycling proteins bearing the carboxyl-terminal sequence KDEL (single-letter amino acid code) to the endoplasmic reticulum, following their loss from that organelle by the process of forward transport']
['The lumenal endoplasmic reticulum (ER) proteins carry a specific sorting signal which enables their retrieval from multiple post-ER compartments (up to the TGN along the exocytotic pathway), back to the ER. The most typical such signal is the carboxyl-terminal Lys-Asp-Glu-Leu (KDEL), which is bound by a KDEL receptor in the Golgi apparatus, as well as in the intermediate compartment. Thus KDEL functions as a retrieval signal of lumenal ER proteins from Golgi to ER.']
['the carboxyl-terminal Lys-Asp-Glu-Leu (KDEL)']