Protein Conformational Changes in the Bacteriorhodopsin Photocycle: Comparison of Findings from Electron and X-Ray Crystallographic Analyses

Light-driven conformational changes in the membrane protein bacteriorhodopsin have been studied extensively using X-ray and electron crystallography, resulting in the deposition of >30 sets of coordinates describing structural changes at various stages of proton transport. Using projection difference Fourier maps, we show that coordinates reported by different groups for the same photocycle intermediates vary considerably in the extent and nature of conformational changes. The different structures reported for the same intermediate cannot be reconciled in terms of differing extents of change on a single conformational trajectory. New measurements of image phases obtained by cryo-electron microscopy of the D96G/F171C/F219L triple mutant provide independent validation for the description of the large protein conformational change derived at 3.2 Å resolution by electron crystallography of 2D crystals, but do not support atomic models for light-driven conformational changes derived using X-ray crystallography of 3D crystals. Our findings suggest that independent determination of phase information from 2D crystals can be an important tool for testing the accuracy of atomic models for membrane protein conformational changes

Circulating Tumor Cell Count Can Be a Useful Prognostic Factor in Lung Resection via Cardiopulmonary Bypass

Tumor resection with cardiopulmonary bypass (CPB) remains controversial in the field of oncology. Here, we present a 57-year-old male patient with locally advanced squamous cell carcinoma. The tumor was located in the left hilum and invaded the left atrium. Complete resection, left pneumonectomy combined with partial left atrium resection, was achieved using CPB. We evaluated the circulating tumor cell (CTC) counts, as a surrogate for micrometastasis, in peripheral blood and the CPB circuit. Both CTC counts were 0, which could indicate local disease without micrometastasis. CTC count may be a useful indicator for tumor resection with CPB in lung cancer