The targeting pathway of Escherichia coli presecretory and integral membrane proteins is specified by the hydrophobicity of the targeting signal

AUTOR(ES)

Lee, Hin C.

FONTE

The National Academy of Sciences

RESUMO

Previous studies have demonstrated that presecretory proteins such as maltose binding protein (MBP) and outer membrane protein A (OmpA) are targeted to the Escherichia coli inner membrane by the molecular chaperone SecB, but that integral membrane proteins are targeted by the signal recognition particle (SRP). In vitro studies have suggested that trigger factor binds to a sequence near the N terminus of the mature region of OmpA and shunts the protein into the SecB pathway by blocking an interaction between SRP and the signal peptide. By contrast, we have found that the targeting pathway of a protein under physiological conditions is dictated by the composition of its targeting signal. Replacement of the MBP or OmpA signal peptide with the first transmembrane segment of AcrB abolished the dependence on SecB for transport and rerouted both proteins into the SRP targeting pathway. More modest alterations of the MBP signal peptide that simply increase its hydrophobicity also promoted SRP binding. Furthermore, we obtained evidence that SRP has a low affinity for typical signal peptides in vivo. These results imply that different classes of E. coli proteins are targeted by distinct pathways because bacterial SRP binds to a more restricted range of targeting signals than its eukaryotic counterpart.

Documentos Relacionados

• Differential use of the signal recognition particle translocase targeting pathway for inner membrane protein assembly in Escherichia coli
• The Structure of Multiple Polypeptide Domains Determines the Signal Recognition Particle Targeting Requirement of Escherichia coli Inner Membrane Proteins
• Physiological Basis for Conservation of the Signal Recognition Particle Targeting Pathway in Escherichia coli
• The affinity of signal recognition particle for presecretory proteins is dependent on nascent chain length.
• Targeting of signal sequenceless proteins for export in Escherichia coli with altered protein translocase.