RESUMEN
Cyanobacteriochromes (CBCRs) are members of the phytochrome superfamily of photosensor proteins that bind a bilin chromophore. CBCRs exhibit substantial diversity in their absorption wavelengths through a variety of bilin-protein interactions. RcaE is the first discovered cyanobacteriochrome as a regulator of chromatic acclimation, where cyanobacteria optimize the absorption wavelength of their photosynthetic antenna. RcaE undergoes a reversible photoconversion between a green-absorbing (Pg) and a red-absorbing (Pr) states, where the bilin chromophore adopts a deprotonated C15-Z,anti and a protonated C15-E,syn structures, respectively. This photocycle is designated as "protochromic photocycle" as the change of the bilin protonation state is responsible for the large absorption shift. With the guidance of recently determined Pg and Pr structures of RcaE, in this study, we investigated bilin-chromophore interaction by site-directed mutagenesis on three key residues referred to as a protochromic triad and also other conserved residues interacting with the bilin. Among the protochromic triad residues, Glu217 and Lys261 are critical for the formation of the Pr state, while Leu249 is critical for the formation of both Pg and Pr states. Substitution in other conserved residues, including Val218, Phe219, and Pro220 in the wind-up helix and Phe252, Phe214, and Leu209 in a part of the bilin-binding pocket, had less substantial effects on the spectral sensitivity in RcaE. These data provide insights into our understanding of the bilin-chromophore interaction in the protochromic photocycle and also its evolution in the CBCRs.
RESUMEN
A 33-year-old woman was referred to Iida Municipal Hospital because of left back pain. Computed tomography showed a tumor (17 x 11 x 10 cm) in the left retroperitoneal space. T1- and T2-weighted magnetic resonance imaging showed an inhomogeneous mass with marginal blood vessels. The tumor was resected via lumbar oblique incision with the thoraco-abdominal approach. The tumor weighed 1800 g and consisted of nests of 5-100 large, loosely arranged, polygonal cells, surrounded by capillaries, resembling alveoli. The tumor cells were rich in cytoplasm, containing periodic acid-Schiff- and diastase-positive granules and typical crystals. The pathological diagnosis was alveolar soft-part sarcoma (ASPS). Alveolar soft-part sarcoma is a rare soft-tissue tumor that accounts for approximately 0.5-1% of soft-tissue sarcomas. Such tumors originating in the retroperitoneal space are extremely rare. Herein is reported a case of ASPS of the retroperitoneum with radiological and pathological findings.
