Humboldt-Universität zu Berlin - Institut für Biologie

Zelluläre Biochemie

Portrait AG-Leiter

Prof. Dr. Thomas Sommer


The accumulation of misfolded or damaged proteins can perturb protein homeostasis. Cells have developed powerful protein quality control (PQC) networks that counteract such damage in a compartment-specific manner. The endoplasmic reticulum (ER) is an organelle through which a significant proportion of proteins travel. It contains an array of molecular chaperones, which help proteins to mature. Nevertheless, a considerable fraction of all newly synthesized polypeptides fail to attain their native conformation. We want to understand how quality control pathways selectively dispose aberrant proteins without jeopardizing correctly folded polypeptides. In the ER, misfolded proteins are recognized by ubiquitin ligase complexes anchored in the ER membrane. Selected substrates of this pathway are exported from the ER in a process termed protein dislocation. Subsequently, substrates are ubiquitylated and degraded by cytoplasmic 26S proteasomes. This process is referred to as ER Associated Protein Degradation (ERAD).

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