Corticostatin-3 precursor

Transit sequences of chloroplast-destined precursor proteins are phosphorylated on a serine or threonine residue. The amino acid motif around the phosphorylation site is related to the phosphopeptide binding motif for 14-3-3 proteins. Plant 14-3-3 proteins interact specifically with wheat germ lysate-synthesized chloroplast precursor proteins and require an intact phosphorylation motif within the transit sequence. Chloroplast precursor proteins do not interact with 14-3-3 when synthesized in the heterologous reticulocyte lysate. In contrast, a precursor protein destined for plant mitochondria was found to be associated with 14-3-3 proteins present in the reticulocyte lysate but not with 14-3-3 from wheat germ lysate. This indicates an unrecognized selectivity of 14-3-3 proteins for precursors from mitochondria and plastids in plants in comparison to fungi and animals. The heterooligomeric complex has an apparent size of 200 kD. In addition to the precursor protein, it contains 14-3-3 (probably as a dimer) and a heat shock protein Hsp70 isoform. Dissociation of the precursor complex requires ATP. Protein import experiments of precursor from the oligomeric complex into intact pea chloroplasts reveal three- to fourfold higher translocation rates compared with the free precursor, which is not complexed. We conclude that the 14-3-3-Hsp70-precursor protein complex is a bona fide intermediate in the in vivo protein import pathway in plants.

Hematogones were initially described as mysterious cells in bone marrow smears more than 70 years ago. These cells are normal bone marrow B-lymphocyte precursors with properties that overlap those of lymphoblasts. Their morphological and immunological features are described here with an update on the knowledge of hematogones in hematological and non-hematological disorders.

A gluconeogenic precursor is a biochemical compound acted on by a gluconeogenic pathway enabling the net synthesis of glucose. Recognized gluconeogenic precursors in fasting placental mammals include glycerol, lactate/pyruvate, certain amino acids, and odd-chain length fatty acids. Each of these precursors is capable of contributing net amounts of carbon to glucose synthesis via the tricarboxylic acid cycle (TCA cycle) because they are anaplerotic, that is, they are able to increase the pools of TCA cycle intermediates by the contribution of more carbon than is lost via carbon dioxide. The net synthesis of glucose from even-chain length fatty acids (ECFAs) in fasting placental mammals, via the TCA cycle alone, is not possible because equal amounts of carbon are lost via carbon dioxide as is contributed from fatty acid oxidation via acetyl-CoA. Therefore, ECFAs do not meet the criteria to be recognized as a gluconeogenic precursor via the TCA cycle alone. ECFAs are gluconeogenic precursors in organisms with a functioning glyoxylate cycle, which enables the net contribution of carbon to the intermediates of the TCA cycle from ECFAs and the net synthesis of glucose. The net conversion of ECFAs to glucose in fasting placental mammals via C3 metabolism of acetone may be a competent though inefficient metabolic path by which ECFA could be considered a gluconeogenic precursor. Defining a substrate as a gluconeogenic precursor requires careful articulation of the definition, organism, and physiologic conditions under consideration.