Abstract
YidC has been identified recently as an evolutionary conserved factor that is involved in the integration of inner membrane proteins (IMPs) in Escherichia coli. The discovery of YidC has inspired the reevaluation of membrane protein assembly pathways in E. coli. In this study, we have analyzed the role of YidC in membrane integration of a widely used model IMP, leader peptidase (Lep). Site-directed photocross-linking experiments demonstrate that both YidC and SecY contact nascent Lep very early during biogenesis, at only 50-amino acid nascent chain length. At this length the first transmembrane domain (TM), which acquires a type I topology, is not even fully exposed outside the ribosome. The pattern of interactions appears dependent on the position of the cross-linking probe in the nascent chain. Upon elongation, nascent Lep remains close to YidC and comes into contact with lipids as well. Our results suggest a role for YidC in both the reception and lipid partitioning of type I TMs.
Highlights
Most Escherichia coli inner membrane proteins (IMPs)1 require the signal recognition particle (SRP) and its receptor FtsY for efficient routing to the inner membrane [1]
leader peptidase (Lep) H1 Interacts with YidC from the Initial Insertion Step— Lep, the major signal peptidase in E. coli, was used as a model protein to investigate the earliest stages of IMP insertion in vitro
Lep has been shown to interact with SRP in vitro [18] and to depend on SRP for efficient targeting to the inner membrane in vivo [19]
Summary
Most Escherichia coli inner membrane proteins (IMPs)1 require the signal recognition particle (SRP) and its receptor FtsY for efficient routing to the inner membrane [1]. The pattern of interactions appears dependent on the position of the cross-linking probe in the nascent chain. The precise pattern of interactions appeared dependent on the position of the crosslinking probe in the nascent chain, suggesting an ordered insertion into an oligomeric YidC/Sec structure.
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