Solution Structure of LC4 Transmembrane Segment of CCR5

CC-chemokine receptor 5 (CCR5) is a specific co-receptor allowing the entry of human immunodeficiency virus type 1 (HIV-1). The LC4 region in CCR5 is required for HIV-1 entry into the cells. In this study, the solution structure of LC4 in SDS micelles was elucidated by using standard 1H two-dimensional NMR spectroscopy, circular dichroism, and fluorescdence quenching. The LC4 structure adopts two helical structures, whereas the C-terminal part remains unstructured. The positions in which LC4 binds to the HIV-1 inhibitory peptide LC5 were determined by docking calculations in addition to NMR data. The poses showed the importance of the hydrophobic interface of the assembled structures. The solution structure of LC4 elucidated in the present work provides a structural basis for further studies on the HIV-1 inhibitory function of the LC4 region

NMR-Based Detection of Hydrogen/Deuterium Exchange in Liposome-Embedded Membrane Proteins.

Membrane proteins play key roles in biology. Determination of their structure in a membrane environment, however, is highly challenging. To address this challenge, we developed an approach that couples hydrogen/deuterium exchange of membrane proteins to rapid unfolding and detection by solution-state NMR spectroscopy. We show that the method allows analysis of the solvent protection of single residues in liposome-embedded proteins such as the 349-residue Tom40, the major protein translocation pore in the outer mitochondrial membrane, which has resisted structural analysis for many years.peerReviewe

Interferon-alpha promotes the anti-proliferative effect of gefitinib (ZD 1839) on human colon cancer cell lines

Objective: Interferon-α (IFNα) treatment is associated with up-regulation of epidermal growth factor receptor (HER1/EGFR) expression and marked growth inhibition of colon cancer cell lines in vitro. We aimed to determine the effect of combining IFNα and gefitinib on colon cancer cell line growth. Methods: A panel of nine colon cancer cell lines were characterised for expression of HER1/ EGFR and then treated with gefitinib alone, or IFNα alone, or IFNα plus gefitinib, following a pre-treatment using vehicle or IFNα. Crystal violet staining and flow cytometry were used to assess cell proliferation and expression of HER1/EGFR. The indexes and statistical assays were used to evaluate significant differences between treatment groups against vehicle control. Results: All cell lines except SW620 were HER1/EGFR positive. IFNα treatment was associated with significant up-regulation of cell surface HER1/EGFR expression in all HER1/EGFR-positive cell lines except KM12SM. Concurrent treatment with IFNα and gefitinib, or IFNα pre-treatment followed by gefitinib, or IFNα pre-treatment followed by a combination of IFNα plus gefitinib, additively or supra-additively/synergistically enhanced the sensitivity of the seven HER1/EGFR-up-regulated cell lines. Conclusion: IFNα improves the anti-proliferative effect of EGFR inhibition in colorectal cancer cell lines. This approach may have clinical implications for improving treatment based on targeting of HER1/EGFR