Comparative XANES study of serotransferrin and ovotransferrin at Cu K-edge: evidence of interactions among the metal sites

The Cu site structure of human serotransferrin and hen ovotransferrin using XANES spectroscopy has been investigated. Although the transferrin family proteins have been extensively studied, the results reported herein are the first concerning the structure of the metal site in C-terminal and N-terminal in the whole protein. Our structural data show that these proteins differ with regard to the independence of the two binding sites and the geometry of copper coordination, ranging from a poorly to a significantly distorted octahedron.     

Molecular diversity of L-type calcium channels. Evidence for alternative splicing of the transcripts of three non-allelic genes

The diversity of L-type calcium channels was probed using the polymerase chain reaction and primers based on regions conserved in the L-type skeletal muscle (CaCh 1) and cardiac calcium channels (CaCh 2). Related sequences were amplified from human heart, hamster heart, rabbit heart, mouse ovary, mouse BC3H1 cells, and hamster insulin-secreting (HIT) cells. Sequencing of various clones revealed the presence of alternate splicing in gene products coding for CaCh 1, CaCh 2, and a related calcium channel. This related gene product, which we refer to as neuroendocrine or CaCh 3, is expressed in brain and endocrine cells. The diverse products can be explained by the use of alternate exons of equal size, which account for changes in amino acid composition, in combination with an alternate splice acceptor site or an exon skipping event, which produces channels of variable length. Four variants were defined for the gene 3 product, subtypes 3a, 3b, 3c, and 3d that differed in both the sequence of the third membrane spanning segment of the fourth repeat unit (IVS3) and in the size of the linker between this and the fourth membrane spanning segment (IVS4). Three CaCh 2 variants were cloned, subtypes 2a, 2c, and 2d, that are homologous to the a, c, and d variants of CaCh 3. For the skeletal muscle calcium channel only two variants were isolated. They are homologous to those of the a and c subtypes of CaCh 2 or 3, in that they differ only in the size of the IVS3 to IVS4 linker. These results demonstrate that calcium channel diversity is created by both the expression of distinct genes and the alternate splicing of these genes.     

Distribution of G1m(1), G1m(2) and G3m(5) allotypes in Aragon.

The distribution of G1m(1), G1m(2) and G3m(5) allotypes was studied in 700 unrelated individuals from Aragon (North-East Spain). The Gm haplotype frequencies were similar to those reported in French areas next to Aragon.     

Distribution of glutathione transferases in Gram-positive bacteria and Archaea

Glutathione transferases (GSTs) have been widely studied in Gram-negative bacteria and the structure and function of several representatives have been elucidated. Conversely, limited information is available about the occurrence, classification and functional features of GSTs both in Gram-positive bacteria and in Archaea. An analysis of 305 fully-sequenced Gram-positive genomes highlights the presence of 49 putative GST genes in the genera of both Firmicutes and Actinobacteria phyla. We also performed an analysis on 81 complete genomes of the Archaea domain. Eleven hits were found in the Halobacteriaceae family of the Euryarchaeota phylum and only one in the Crenarchaeota phylum. A comparison of the identified sequences with well-characterized GSTs belonging to both Gram-negative and eukaryotic GSTs sheds light on their putative function and the evolutionary relationships within the large GST superfamily. This analysis suggests that the identified sequences mainly cluster in the new Xi class, while Beta class GSTs, widely distributed in Gram-negative bacteria, are under-represented in Gram-positive bacteria and absent in Archaea.     

Cryptolepiota, a new sequestrate genus in the Agaricaceae with evidence for adaptive radiation in western North America

Phylogenetic analyses based on nLSU and ITS sequence data indicate that the sequestrate genus Gigasperma is polyphyletic. Gigasperma cryptica, which is known only from New Zealand, has affinities with the Cortinariaceae whereas G. americanum and two additional undescribed taxa from western North America are derived from Lepiota within the Agaricaceae. The three North American taxa appear to be recently evolved and are closely related. They occur in similar environments and form a well supported clade indicating that adaptive radiation has occurred within this group of fungi. An independent genus with sequestrate fructifications, Cryptolepiota is proposed to accommodate the three species in this clade. Cryptolepiota microspora and C. mengei are described as new, and G. americanum is transferred to Cryptolepiota. Gigasperma cryptica is illustrated and compared with the species of Cryptolepiota.