The C‐terminus of CsgE Is Involved In Preventing Protein Aggregation

作者：Isamar Aranda, Ashwag Binmahfooz, Kuldeep H. Kaur, Huda Rabi, Lisa I-Ching Yeh, Sajith Jayasinghe · 发表于：The FASEB Journal · 年份：2018 · DOI：10.1096/fasebj.2018.32.1_supplement.lb49 · 研究领域：Escherichia coli research studies、Hepatitis B Virus Studies、Prion Diseases and Protein Misfolding

Gram‐negative bacteria, such as E.coli and Salmonella, contain proteinaceous, hair‐like, cell surface organelles known as curli. Curli serve to facilitate cell‐cell interactions and are essential for host cell colonization. Curli assembly involves six proteins, CsgA, CsgB, CsgC, CsgE, CsgF, and CsgG. CsgE and CsgF act as chaperones to prevent the premature aggregation of CsgA and CsgB which are the main protein components of Curli. CsgE and CsgF help transport CsgA and CsgB proteins to the cell surface, where CsgA and CsgB begin to assemble to form Curli. We have observed that CsgE is able to inhibit the aggregation of CsgA, as well as human islet amyloid polypeptide (hIAPP), an amyloidogenic polypeptide that is unrelated to curli. We used four different mutants of CsgE (34C, 58C, 99C and 119C) where the wild type residue at the respective position was replaced by a cysteine, and labeled with the fluorophore IASEDANS together with fluorescence quenching to determine the ability of CsgE to interact with the non‐aggregating rat Islet Amyloid Polypeptide (rIAPP). rIAPP differs from hIAPP by only three amino acids, but does not aggregate to form amyloid and was used to reduce the complicating effects of hIAPP aggregation. In the absence of rIAPP IAEDANS labeled at positions 34, 58, 99 and 119 gave Stern‐Volmer quenching constants of 9.6, 9.2, 12.1, and 7.6 respectively, while in the presence of rIAPP these values were 9.7, 8.7, 12.4, and 6.5. The significant reduction in the quen...