Ribosomes that exist freely in the cytosol or those attached to the ER are intrinsically the same in their translational properties. ER-bound
ribosomes are responsible for the production of secretory proteins and integral ER, Golgi, lysosomal, and plasma membrane spanning proteins.
Such proteins contain signal sequences that direct their synthesis to the ER membrane. As the nascent polypeptide emerges from the
ribosome, a signal recognition particle (SRP) binds to the signal sequence and serves to couple the ribosome to the protein-translocating
machinery in the ER membrane. Although the SRP is a 325 kDa ribonucleoprotein, its 54 kDa subunit (SRP54) mediates interaction with, and
targeting of, the nascent protein to the ER. Via its C-terminal M-domain, SRP54 associates with the nascent protein and inhibits its
elongation. This complex binds to the SRP receptor on the ER, the ribosome is delivered to the translocation machinery, SRP is released, and
elongation resumes. Targeting and insertion are tightly coupled to a GTPase cycle that involves SRP54 and SRP receptor. Although the
mechanisms are unclear, release of SRP from the ER-bound complex requires GTP hydrolysis.
原厂资料:
注意事项:
1.Since applications vary, each investigator should titrate the reagent to obtain optimal results.
2.Caution: Sodium azide yields highly toxic hydrazoic acid under acidic conditions. Dilute azide compounds in running water before discarding to avoid accumulation of potentially explosive deposits in plumbing.