Exploring the capacity of trigger factor to function as a shield for ribosome bound polypeptide chains

Edited by Felix Wieland

Received 18 October 2005; received in revised form 18 November 2005; accepted 21 November 2005. published online 05 December 2005.

Abstract

Ribosome-bound trigger factor (TF) is the first chaperone encountered by a nascent polypeptide chain in bacteria. TF has been proposed to form a cradle-shaped shield for nascent chains up to ∼130 residues to fold in a protected environment upon exit from the ribosome. We report that nascent chains of luciferase up to 280 residues in length are relatively protected by TF against digestion by proteinase K. In contrast, nascent chains of the constitutively unstructured protein α-synuclein were not protected, although they were in close proximity to TF by crosslinking. Thus, TF is not a general shield for nascent chains. Protease protection appears to depend on a hydrophobic interaction of TF with nascent polypeptides.

Keywords: Trigger factor, Ribosome nascent chain complex, Proteinase K, Luciferase, α-Synuclein, Molecular chaperones

a Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany

b Department of Medical Biochemistry and Genetics, Texas A&M University System Health Science Center, College Station, TX 77843-1114, USA

c Department of Chemistry, Texas A&M University, College Station, TX 77843, USA

d Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA

Corresponding authors. Fax: +49 89 8578 2211.

PII: S0014-5793(05)01420-1

doi:10.1016/j.febslet.2005.11.050

15 of 63