Cover Picture: Proteomics 17'09

Blue on blue Few protein analysis techniques approach the resolution of, or the tedium of preparing for, large‐format 2‐D gel electrophoresis. Then you find the first dimension gives poor resolution of samples rich in membrane‐bound proteins. A relatively new modification of the classic standard IPG method for analysis of membrane‐bound proteins is “Blue Native” gel electrophoresis. BN‐PAGE incorporates a dye such as Coomassie Blue G‐250 into membrane complexes to give them an electrophoretic mobility roughly proportional to their size. Conventionally SDS‐PAGE is used for a second dimension. Wessels et al . instead used in‐gel digestion followed by LCMS/MS for a higher resolution second dimension. The modified method gave faster identification of overlapping proteins and was able to detect assembly intermediates and transient interactions.. Wessels, H. J. C. T. et al. , Proteomics 2009, 9 , 4221–4228. Making sense of senescence The ripening (senescence) of fruit is one of the final steps in the life cycle of a plant. It is also the step that makes many edible fruits palatable or sweet and so is of economic significance as well. Since ripening is an oxidative step, Qin et al . examine the effect of reactive oxygen species (ROS) on the proteome of apple mitochondria. Accelerating senescence by exposure to 100% oxygen led to under‐expression of Mn superoxide dismutase (MnSOD), an enzyme characteristic of mitochondrial membranes and primary scavenger of free radicals. In addition to previously recognized enzymes, two new spots of unknown function were identified that will require further study. High oxygen also increased the frequency of carbonylation of selected proteins. Reducing the oxygen to 2% markedly reduced the rate of senescence and decreased the number of proteins up‐ or down‐regulated. Qin, G. et al. , Proteomics 2009, 9 , 4241–4253. Pleckstrin, pleckstrin, wherefore art thou? It may not be quite as romantic as Juliet awaiting Romeo, but pleckstrin is rather shy about holding hands in public. Platelets lacking pleckstrin do not aggregate, secrete granules or polymerize actin, yet no direct signals between pleckstrin and actin have been seen. Pleckstrin is the major target of protein kinase C (PKC) in platelets and many platelet stimuli correlate with phosphorylation. Baig et al . set off to find out how the secret messages were being passed. They used recombinant and pseudo‐phosphorylated pleckstrin, immunoprecipitation, GST‐pulldown assays, PKC‐activated and PKC‐inhibited platelets, and quad‐TOF MS. Several unusual protein associations were found but no direct association with actin. The authors propose an indirect link between actin and pleckstrin (mediated by Juliet's maid), possibly through a‐actinin, factor XIIIA, moesin, radixin, or 17‐b‐hydroxysteroid dehydrogenase 4 Baig, A. et al. , Proteomics 2009, 9 , 4254–4258.