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. 1998 May;7(5):1195–1200. doi: 10.1002/pro.5560070514

Calorimetric analyses of the interaction between SecB and its ligands.

L L Randall 1, T B Topping 1, D Suciu 1, S J Hardy 1
PMCID: PMC2144013  PMID: 9605324

Abstract

SecB is a chaperone in Escherichia coli dedicated to export of proteins from the cytoplasm to the periplasm and outer membrane. It functions to bind and deliver precursors of exported proteins to the translocation apparatus before they fold into their native structures, thus maintaining them in a competent state for translocation across the membrane. The natural ligands of SecB are precursor proteins containing leader sequences. There are numerous reports in the literature indicating that SecB does not specifically recognize the leader peptides. However, two published investigations have concluded that the leader peptide is the recognition element (Watanabe M, Blobel G. 1989. Cell 58:685-705; Watanabe M, Blobel G. 1995. Proc Natl Acad Sci USA 92:10133-10136). In this work we use titration calorimetry to show that SecB binds two physiological ligands, which contain leader sequences, with no higher affinity than the same molecules lacking their leader sequences. Indeed, for one ligand the presence of the leader sequence reduces the affinity. Therefore, it can be concluded that the leader sequence provides no positive contribution to the binding energy.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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