Infected Thoracic Aortic Aneurysm Caused by Helicobacter cinaedi.

The causative organism is not identified in some cases of infected aneurysms, a life-threatening condition. A 68-year-old man presented with chest/back pain and a 1-year history of intermittent fever and fatigue. Computed tomography revealed a thoracic aortic aneurysm. After several negative blood cultures, he was eventually diagnosed with an infected aneurysm caused by Helicobacter cinaedi via gene analysis of an aortic tissue specimen. As H. cinaedi is a low-virulence bacterium, infection with this pathogen should be suspected in cases of aortic aneurysms with unidentified causative organism and a long history of subjective symptoms. Detailed examinations, including polymerase chain reaction, should be conducted in such cases.

Assay of photoinhibition of photosystem II and protease activity.

Under light-stress conditions, the photosystem (PS)II reaction center D1 protein is photo-damaged. The damage to the D1 protein is induced by singlet oxygen molecules and endogenous free radicals generated by the photochemical reactions of PSII. To maintain PSII activity, the oxidatively damaged D1 protein is replaced by a newly synthesized protein. Thus, degradation and removal of the photodamaged D1 protein in PSII are essential steps for maintaining the viability of PSII. In the present chapter, we describe the method to induce photoinhibition of PSII both in vitro and in vivo, and also the method to assay the processes closely related to the photoinhibition, including degradation of the damaged D1 protein and its crosslinking with the neighboring polypeptides. The method to analyze the protease activity in the stroma that recognizes and digests the crosslinked products of the D1 protein generated by the light stress is also described.

Dynamic Interaction between the D1 protein, CP43 and OEC33 at the lumenal side of photosystem II in spinach chloroplasts: evidence from light-induced cross-Linking of the proteins in the donor-side photoinhibition.

During the donor-side photoinhibition of spinach photosystem II, the reaction center D1 protein cross-linked with the antenna chlorophyll binding protein CP43 of photosystem II lacking the oxygen-evolving complex (OEC) subunit proteins. The cross-linking did not occur upon illumination of photosystem II samples that retained the OEC33, nor when OEC33-depleted photosystem II samples were reconstituted with the OEC33 prior to illumination. These results suggest that the D1 protein, CP43 and the OEC33 are located in close proximity at the lumenal side of photosystem II, and that the OEC33 suppresses the unnecessary contact between the D1 protein and CP43. Previously we presented data showing the D1 protein located adjacent to CP43 on the stromal side of photosystem II [Ishikawa et al. (1999) BIOCHIM: Biophys. Acta 1413: 147]. The present data suggest that the spatial arrangement of the D1 protein and CP43 at the lumenal side of photosystem II in spinach chloroplasts is similar to that at the stromal side of photosystem II and is consistent with the assignment of these proteins recently proposed on the crystal structures of the photosystem II complexes from cyanobacteria [Zouni et al. (2001) Nature 409: 739, Kamiya and Shen 2003 PROC: Natl. Acad. Sci. USA, 100: 98]. Moreover, the data suggest that the binding condition and positioning of the OEC33 in the photosystem II complex from higher plants may be different from those in cyanobacteria.