Molecular localization of a redox-modulated process regulating plant mitochondrial electron transport

Using in organellar assays, we found that significant tobacco alternative oxidase (AOX) activity is dependent on both reduction of a putative regulatory disulfide bond and the presence of pyruvate, which may interact with a Cys sulfhydryl. This redox modulation and pyruvate activation thus may be important in determining the partitioning of electrons to AOX in vivo. To investigate these regulatory mechanisms, we generated tobacco plants expressing mutated AOX proteins. Mutation of the most N-terminal Cys residue (Cys-126) to an Ala residue produced an AOX that could not be converted to the disulfide-linked form, thus identifying this Cys residue as being responsible for redox modulation. Although this mutation might be expected to produce an AOX with constitutive high activity in the presence of pyruvate, we found it to have minimal in organellar activity in the presence of pyruvate. Nonetheless, the Cys-126 mutation did not appear to have compromised the catalytic function of AOX, given that cells expressing the protein displayed high rates of cyanide-resistant respiration in vivo. The striking difference between in vivo and in organellar results suggests that an additional mechanism(s), as yet unidentified by in organellar assays, may promote activity in vivo. Mutation of the Cys residue nearest the presumptive active site (Cys-176) to an Ala residue did not prevent disulfide bond formation or affect the ability of AOX to be stimulated by pyruvate, indicating that this Cys residue is involved in neither redox modulation nor pyruvate activation.     

GO Explorer: A gene-ontology tool to aid in the interpretation of shotgun proteomics data

Background  

Spectral counting is a shotgun proteomics approach comprising the identification and relative quantitation of thousands of proteins in complex mixtures. However, this strategy generates bewildering amounts of data whose biological interpretation is a challenge.     

The endangered maned sloth Bradypus torquatus of the Brazilian Atlantic forest: a review and update of geographical distribution and habitat preferences

• 1 The endemic maned sloth Bradypus torquatus is globally threatened due to deforestation, habitat fragmentation and isolation of populations. Despite increased interest in the species in recent years, information on its geographic distribution is limited and is derived mainly from a few museum species and from a survey based mostly on interviews carried out more than 20 years ago. Information on its habitat and altitudinal preferences is lacking. We therefore compile, update and review all occurrence records of this species using geographical information system (GIS) tools and produce a distribution map for the species.
• 2 Our compilation totalled 188 occurrence records, of which 130 (69%) were considered confirmed (museum specimens or individuals captured or seen in the field), most of which (62%) were restricted to the states of Bahia and central‐south Espírito Santo (29%). The species occurs predominantly in ombrophilous forest (80%), from sea level to 1290m, but mainly (79%) below 200m altitude.
• 3 We used GIS techniques and the alpha shape algorithm to calculate the extent of occurrence of the species and compared the resulting map with distribution maps available in the literature. We found a great deal of variation in distribution area shape and an almost two‐fold variation in distribution area size among sources.
• 4 We confirmed the existence of a main distribution gap between southern Bahia and northern Espírito Santo and discovered a second smaller gap between southern Espírito Santo and northern Rio de Janeiro.
• 5 We also confirmed that B. torquatus is sympatric with the common three‐toed sloth Bradypus variegatus in a large part of the Atlantic forest and that the two species are syntopic in at least 11 locations.