Several algorithms have been described in the literature for protein identification by searching a sequence database using mass spectrometry data. In some approaches, the experimental data are peptide molecular weights from the digestion of a protein by an enzyme. Other approaches use tandem mass spectrometry (MS/MS) data from one or more peptides. Still others combine mass data with amino acid sequence data. We present results from a new computer program, Mascot, which integrates all three types of search. The scoring algorithm is probability based, which has a number of advantages: (i) A simple rule can be used to judge whether a result is significant or not. This is particularly useful in guarding against false positives. (ii) Scores can be compared with those from other types of search, such as sequence homology. (iii) Search parameters can be readily optimised by iteration. The strengths and limitations of probability-based scoring are discussed, particularly in the context of high throughput, fully automated protein identification.

Probability-based protein identification by searching sequence databases using mass spectrometry data.

http://nhjy.hzau.edu.cn/kech/ssyy/pdf/drought/4.PDF

Photosynthesis under drought and salt stress: regulation mechanisms from whole plant to cell

The three-dimensional structure of acetylcholinesterase from Torpedo californica electric organ has been determined by x-ray analysis to 2.8 angstrom resolution. The form crystallized is the glycolipid-anchored homodimer that was purified subsequent to solubilization with a bacterial phosphatidylinositol-specific phospholipase C. The enzyme monomer is an alpha/beta protein that contains 537 amino acids. It consists of a 12-stranded mixed beta sheet surrounded by 14 alpha helices and bears a striking resemblance to several hydrolase structures including dienelactone hydrolase, serine carboxypeptidase-II, three neutral lipases, and haloalkane dehalogenase. The active site is unusual because it contains Glu, not Asp, in the Ser-His-acid catalytic triad and because the relation of the triad to the rest of the protein approximates a mirror image of that seen in the serine proteases. Furthermore, the active site lies near the bottom of a deep and narrow gorge that reaches halfway into the protein. Modeling of acetylcholine binding to the enzyme suggests that the quaternary ammonium ion is bound not to a negatively charged "anionic" site, but rather to some of the 14 aromatic residues that line the gorge.

https://science.sciencemag.org/content/sci/253/5022/872.full.pdf

Atomic structure of acetylcholinesterase from Torpedo californica: a prototypic acetylcholine-binding protein

Synthesis, structure and properties of polyhydroxyalkanoates: biological polyesters

ROS signaling: the new wave?

In plants de novo fatty acid biosynthesis occurs within the plastids. The first committed step in this process is the ATP dependant carboxylation of acetyl CoA to malonyl CoA. This is catalysed by acetyl CoA carboxylase (ACCase, EC 6.4.1.2), which is believed to be a key regulatory enzyme in this process (Post Beittenmiller et al. 1992). Two forms of ACCase have now been identified in dicots. A single large multifunctional polypeptide (ACCase I), and a multipeptide prokaryotic form (ACCase II). Subcellular localisation studies on ACCase II (Alban et al. 1995; Shorrosh et al. 1995; Elborough et al. 1996) indicate a chloroplast localisation. This is suggestive of a role in de novo fatty acid biosynthesis. The extrachloroplastic localisation (Alban et al 1994) of ACCase I suggests a different role. ACCase I is responsive to UV and fungal elicitors possibly indicating a role in cytosolic fatty acid elongation, and wax and flavanoid biosynthesis.

Transgenic Modification of Acetyl CoA Carboxylase and ß-Keto Reductase Levels in Brassica Napus Functional and Regulatory Analysis

Il a ete demontre que des isomeres d'acide linoleique conjugues a une premiere liaison double en position 9 cis ou 10 (trans), ajoutee de facon exogene, peuvent etre desatures en position 6 par la cyanobacterie Spirulina platensis. Les metabolites, les acides 6-cis, 9-cis, 11-trans-octadecatrienoiques et 6-;cis, 10-trans, 12-cis-octadecatrienoiques, qui n'ont pas prealablement ete caracterises, ont ete isoles par une combinaison de techniques chromatographiques et les structures confirmees par spectrometrie de masse/chromatographie en phase gazeuse sous forme d'esters de picolinyle et de derives dimethyloxazoline.

Conjugaison d'acides gras et composes associes

Cellular levels of phosphatidylcholine (PC) have been known to be influenced by plant hormones [1] as well as by environmental stimuli such as low temperature [2]. However, little is known about the mechanism of regulation, and biological meanings are open to conjecture. For better understanding of the phenomena, it is essential to clone the gene of interest.

Brassica Napus CTP:Phosphocholine Cytidylyltransferase: Molecular Cloning and Subcellular Localization in Yeast,and Enzyme Characterization

Il est possible de produire des plantes, et en particulier des plantes transgeniques presentant une enzyme du type 2-acyltransferase a partir de Limnanthes presentant une specificite alteree du substrat par comparaison avec l'enzyme originale Par exemple la graine de colza oleagineux Brassica napus peut contenir les deux transgenes de 2-acyltransferase derivant du Limnanthes douglasii permettant de produire de la trierucine La sequence d'ADNc de la 2-acyltransferase du Limnanthes douglasii et sa sequence proteique equivalente sont presentees ici

Sequence d'adn codant pour de la 2-acyltransferase vegetale

Acyl Carrier Protein [ACP] is a small acidic protein which is an essential component of the type 2, dissociable fatty acid synthetase [1]. ACP is synthesised as an apo-protein and posttranslationally modified, by the addition of a 4’ phosphopantetheine [4’PANT] prosthetic group, which is linked to a serine residue by a phosphodiester bond. The amino acid sequence around the modified serine residue is highly conserved [2]. The post—translational modification is catalysed by holo-ACP synthetase [HAS], and this enzyme can also catalyse the direct conversion of apo-ACP to acyl-ACP using acyl-CoA as a source of the both the 4’ PANT and the acyl group [3]. Apart from the role of ACP in fatty acid biosynthesis it is an important component of a number of other reactions which require acyl-transferase steps, these include: membrane derived oligosaccharides, polyketide antibiotics, biotin precursor, and acyl-transfer to glycerol-3-phosphate [E.coli and plants] and lysophosphatidic acid. Additionally acyl-ACPs are the substrates for both thioesterases and soluble desaturases. NMR structures exist for holo-ACP and acyl-ACPs [4] and recently a X-ray crystallographic structure has been reported for a HAS-ACP complex from Bacillus subtilis [5]. In this study we are interested in determining the x-ray structure for an acyl-ACP and have used a combination of recombinant and non-recombinant proteins. Our eventual aim is to obtain structural data on a variety of different acyl-ACPs as well as acyl-ACP’ s complexed to enzymes of lipid metabolism.

Antoni R. Slabas

Papers

Transgenic Modification of Acetyl CoA Carboxylase and ß-Keto Reductase Levels in Brassica Napus Functional and Regulatory Analysis

Conjugaison d'acides gras et composes associes

Brassica Napus CTP:Phosphocholine Cytidylyltransferase: Molecular Cloning and Subcellular Localization in Yeast,and Enzyme Characterization

Sequence d'adn codant pour de la 2-acyltransferase vegetale

Determination of the X-Ray Crystallographic Structure of E.coli Butyryl-ACP