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Haemoglobin, the`honorary enzyme ' [Brunori (1999), Trends Biochem. Sci. 24, 158±161], constitutes a prime prototype for allosteric models. Here, the crystallization and preliminary X-ray analysis of haemoglobin I from the South American ®sh Brycon cephalus are reported. X-ray diffraction data have been collected to 2.5 A Ê resolution using synchrotron radiation (LNLS). Crystals were determined to belong to the space group P6 1 22 and preliminary structural analysis revealed the presence of one dimer () in the asymmetric unit. The structure was determined using standard molecular-replacement techniques.

Abstract:In this work the authors evaluated the expression of cat, glu, cypP450, hsp70 and 18S RNA in Colossoma macropomum following exposure to copper and cadmium by semi-quantitative RT-PCR and quantitative qRT-PCR. In RT-PCR and qRT-PCR hsp70 expression was highest after exposure to copper for 3 hours (h). glu expression increased after exposure to cadmium, regardless of time. cat expression increased after the first hour of exposure to both metals, and decreased after 3 hs. cyp450 expression was higher when compared to controls in exposed fish regardless of metal and exposure time. cyp450 expression after exposure to copper for 3 h was twice that recorded after 1 h. In the presence of cadmium, cyp450 expression was higher in the animals exposed for 1 h and lower at 3 h. Therefore, toxicology tests and biomonitoring based on molecular markers should focus on a set of molecular and/or environmental parameters, rather than isolated markers.

The present work reports our succesfull experience concerning crystallization of four fish hemoglobins from three Brazilian species of Teleosts: Liposarcus anisitsi, Brycon cephalus and Piaractus mesopotamicus. The data shown here is part of a systematic functional and structural study of fish hemoglobins with the aim of better understanding the outstanding range of functional and structural properties exhibited by these proteins. We also present a reduced sparse-matrix method for crystallization of fish hemoglobins, which can reduce the amount of hemoglobin initially used in the crystallization experiments.