How are proteins directed to lysosomes?

Proteins are directed to lysosomes primarily through a specific tagging process known as mannose-6-phosphate tagging. This mechanism is crucial for ensuring that certain enzymes and proteins are correctly sorted and delivered to lysosomes, which are essential organelles for cellular degradation and recycling processes.

During the synthesis of lysosomal enzymes, they are tagged with a mannose-6-phosphate group in the Golgi apparatus. This modification serves as a signal for the transport of these enzymes to lysosomes. The mannose-6-phosphate is recognized by specific receptors that facilitate the packaging of these tagged proteins into transport vesicles. Once the vesicles reach the lysosome, the acidic environment inside the lysosome causes the release of the enzymes from the receptors, allowing them to function in degrading substrates within the lysosome.

The other options do not play a direct role in the targeting of proteins specifically to lysosomes. Phosphorylation is a post-translational modification that can affect protein activity but is not the mechanism used for lysosomal targeting. Ubiquitin tagging is primarily involved in targeting proteins for degradation by the proteasome, which is different from lysosomal degradation. Lastly, ribosomal attachment relates to the translation of proteins and does not pertain to