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The methionine‐rich domain of the 54 kDa subunit of signal recognition particle is sufficient for the interaction with signal sequences.
Author(s) -
Lütcke H.,
High S.,
Römisch K.,
Ashford A.J.,
Dobberstein B.
Publication year - 1992
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1992.tb05199.x
Subject(s) - biology , plant biology , stem cell biology , computational biology , genetics , gene , botany , reproductive technology , embryogenesis
The signal recognition particle (SRP) binds to signal sequences when they emerge from a translating ribosome and targets the complex of ribosome, nascent chain and SRP to the membrane of the rough endoplasmic reticulum (rER) allowing the co‐translational translocation of the nascent chain. By photo‐crosslinking it has been shown that the signal sequence of preprolactin (PPL) only interacts with the methionine‐rich (M) domain of the 54 kDa protein subunit (SRP54) of SRP. Here we show that (i) a signal‐anchor sequence is likewise crosslinked only to the methionine‐rich domain of SRP54, (ii) free SRP54 can interact with signal sequences independently of the other components of SRP, (iii) its M domain suffices to perform this function, and (iv) an essentially intact M domain is required for signal sequence recognition. Alkylation of the N+G domain in intact SRP54 with N‐ethyl maleimide (NEM), but not after cleavage with V8 protease, prevents the binding of a signal sequence to the M domain. This suggests a proximity between the N+G and M domains of SRP54 and raises the possibility that the role of the N+G domain may be to regulate the binding and/or the release of signal sequences.