A survey of Nellore breed based on nine molecular markers.

The Brazilian Nellore is a Bos indicus brees developed from animals imported from india up to the middle of this centry. Due to its high tolerance ti the tropical environment, the Nellore became the most popular beef cattle brees in Brazil. Besidies its importance as pure breed, it has been successfully used in commeercial crosses and in the composition of new breeds. Genetic variability providies the scenario for selection in animal breeding programs. Monitoring this variabilty through molecular marker analysis can be useful to prevent genetic erosion. The objective of this study was to charactize Nellore animals based on restriction fragment lenth polymorphisms (RFLP) and microsatellites.Resum

The Assembly of the Plasmodial PLP Synthase Complex Follows a Defined Course

Background: Plants, fungi, bacteria and the apicomplexan parasite Plasmodium falciparum are able to synthesize vitamin B6 de novo, whereas mammals depend upon the uptake of this essential nutrient from their diet. The active form of vitamin B6 is pyridoxal 5-phosphate (PLP). For its synthesis two enzymes, Pdx1 and Pdx2, act together, forming a multimeric complex consisting of 12 Pdx1 and 12 Pdx2 protomers. Methodology/Principal Findings: Here we report amino acid residues responsible for stabilization of the structural and enzymatic integrity of the plasmodial PLP synthase, identified by using distinct mutational analysis and biochemical approaches. Residues R85, H88 and E91 (RHE) are located at the Pdx1:Pdx1 interface and play an important role in Pdx1 complex assembly. Mutation of these residues to alanine impedes both Pdx1 activity and Pdx2 binding. Furthermore, changing D26, K83 and K151 (DKK), amino acids from the active site of Pdx1, to alanine obstructs not only enzyme activity but also formation of the complex. In contrast to the monomeric appearance of the RHE mutant, alteration of the DKK residues results in a hexameric assembly, and does not affect Pdx2 binding or its activity. While the modelled position of K151 is distal to the Pdx1:Pdx1 interface, it affects the assembly of hexameric Pdx1 into a functional dodecamer, which is crucial for PLP synthesis. Conclusions/Significance: Taken together, our data suggest that the assembly of a functional Pdx1:Pdx2 complex follows

It Takes Two to Tango: Defining an Essential Second Active Site in Pyridoxal 5′-Phosphate Synthase

The prevalent de novo biosynthetic pathway of vitamin B6 involves only two enzymes (Pdx1 and Pdx2) that form an ornate multisubunit complex functioning as a glutamine amidotransferase. The synthase subunit, Pdx1, utilizes ribose 5-phosphate and glyceraldehyde 3-phosphate, as well as ammonia derived from the glutaminase activity of Pdx2 to directly form the cofactor vitamer, pyridoxal 5′-phosphate. Given the fact that a single enzyme performs the majority of the chemistry behind this reaction, a complicated mechanism is anticipated. Recently, the individual steps along the reaction co-ordinate are beginning to be unraveled. In particular, the binding of the pentose substrate and the first steps of the reaction have been elucidated but it is not known if the latter part of the chemistry, involving the triose sugar, takes place in the same or a disparate site. Here, we demonstrate through the use of enzyme assays, enzyme kinetics, and mutagenesis studies that indeed a second site is involved in binding the triose sugar and moreover, is the location of the final vitamin product, pyridoxal 5′-phosphate. Furthermore, we show that product release is triggered by the presence of a PLP-dependent enzyme. Finally, we provide evidence that a single arginine residue of the C terminus of Pdx1 is responsible for coordinating co-operativity in this elaborate protein machinery

Genetic distances among Aberdeen Angus, Canchim, Caracu, Nellore and Simmental beef cattle breeds.

Bovine breeds starded to be selected in the old world, during the 19thcentry. The starting populations werw varieties of cattle adapted by natural selection to the local enviroment. Now a days, a large quantityof spceialized bovine breeds are spread all over the world. Several ofthese are exploited for meat proction in Brazil. The objective of the present work was to investigate the genetic ralationsphip among some of these breeds, representing beef cattle from different categories: Caracu, a European breed adaptded to tropical environment, Simmental, a continental european breed, Aberdeen Angus, a representative of British Isles breeds, Canchim, a crossbred (5/8 Charolais, 3/8 Bos indicus) and Nellore, The most relevant Bos indicus beef cattle breed in Brazil

A study of genetic variability in Canchim (5/8 Charolais, 3/8 Zebu) based on 8 molecular markers.

The canchim is a synthetic beff caattle breed, produced by crosse betwen charolais (Bos taurus) and bos indicus breeds (Zebu). With a genetic composition of 5/8 Charolais + 3/8 zebu, Canchim combines growth ability associated with a bos taurus breed and tolerance to tropical environments that attributed to Zebu breeds. The herd used in this study was formed in 1953 and subjectd to phenotypicc selection for yealing weiht and fertility, under pasture management. Even though the average inbreeding coefficient was kept low by avoiding consaguineous mating (Alencar et al., 1981), genetic variability losses could be ecpected as a result of selection and restricted effective mumber (Ne), since there was no introction of ouside animals. The objective of this study wasto evaluate genetic variability parameters estimated from molecular dara