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#protein retrieval

2 public questions tagged with this topic.

Protein Sorting and Trafficking

How does the KDEL receptor regulate protein retrieval?

ER lumen contains chaperones BiP HSPA5, Grp94 HSP90B1, PDI family, calreticulin that may leak into Golgi during non-selective bulk flow; retention therefore relies on active retrieval not static retention. Soluble residents carry C-terminal KDEL tetrapeptide Lys-Asp-Glu-Leu or variant HDEL. If they escape to cis-Golgi beyond, KDEL receptors family of seven-transmembrane proteins Erd2 in yeast KDELR1-3 in mammals concentrated in Golgi and ERGIC recognize tetrapeptide. Binding strongly pH dependent because histidine residues protonate at mildly acidic Golgi lumen pH 6.0-6.2 stabilizing interacti

Ref: Alberts et al., MBC Chapter 13: KDEL receptor pH-dependent retrieval to ER via COPI.

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Protein Sorting and Trafficking

Proteins with the KDEL signal are retrieved from:

Lumenal residents of endoplasmic reticulum that perform folding, such as BiP/GRP78, protein disulfide isomerase, calreticulin and Grp94, must be retained despite continuous bulk flow to Golgi. Retention is achieved by C-terminal tetrapeptide KDEL or variants HDEL in yeast for soluble proteins and Lys-Lys-X-X or Arg-X-Arg motifs for type I membrane proteins. Escaped proteins reach cis-Golgi and ER-Golgi intermediate compartment where seven-transmembrane KDEL receptor Erd2, actually three isoforms KDELR1-3 in mammals, cycles constitutively between ER and Golgi. At mildly acidic Golgi pH near 6.2

Ref: Alberts et al., Molecular Biology of the Cell, 6th ed., Chapter 12: KDEL Retrieval via Erd2 and COPI Vesicles.

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