Phosphorylation of chloroplast ribulose bisphosphate carboxylase/oxygenase small subunit by an envelope-bound protein kinase in situ

A new protein kinase of the cAMP independent type was found to be bound to the outer envelope membrane of spinach chloroplasts. While stimulated by Mg2+ and inhibited by ADP, the enzyme showed no response to conventional protein substrates and was essentially independent of pH in the physiological (pH 7 to 8) range. The new protein kinase phosphorylated the mature form of the small subunit of ribulose 1,5- bisphosphate carboxylase/oxygenase and, to a lesser extent, an unidentified 24-kDa polypeptide, both of which were bound to the outer envelope membrane. The results suggest that phosphorylation of cytoplasmically synthesized protein constituents of chloroplasts is involved in their transport through the chloroplast envelope membrane barrier

Water And The Flint Hills

Nobody wants rain tonight. But ask yourself, If rain fell here, where would it go? To truly understand a place, you must know something about its water. That’s true for all of Kansas, and it’s certainly true for the Flint Hills

An enzyme synthesizing fructose 2,6-bisphosphate occurs in leaves and is regulated by metabolite effectors

AbstractAn enzyme catalyzing the ATP and fructose 6-phosphate-dependent synthesis of fructose 2,6-bisphosphate, a regulator of glycolysis and gluconeogenesis, has been identified and partially purified from plants, specifically the cytoplasmic fraction of spinach leaf parenchyma cells. The enzyme, designated fructose 6-phosphate, 2-kinase, showed no response to a protein phosphorylation system known to inhibit the corresponding enzyme in mammalian cells, but it responded strikingly to metabolite effectors (Pi, an activator/PGA, an inhibitor) through changes in substrate affinity and maximal velocity. The observed pattern of regulation suggests a role for chloroplasts in controlling cytoplasmic carbon processing

Springs of the Flint Hills

Introduction: Jack Spring is a prairie oasis. Tucked away in southwestern Chase County, it’s only a few miles from the Kansas Turnpike, but a world away in terms of the setting. The spring spills out of dark openings in a limestone bluff, then drops down into a creek choked with bright green watercress. Minnows dart in the water. Leaves rustle in the cottonwoods. Jack Spring is just one of many places in the Flint Hills where, for centuries, water has brought together people, plants, and animals. (Originally published in the 2009 Symphony in the Flint Hills Field Journal.

Springs of the Flint Hills

Jack Spring is a prairie oasis. Tucked away in southwestern Chase County, it\u27s only a few miles from the Kansas Turnpike, but a world away in terms of the setting. The spring spills out of dark openings in a limestone bluff, then drops down into a creek choked with bright green watercress. Minnows dart in the water. Leaves rustle in the cottonwoods

Metabolite-mediated catalyst conversion of PFK and PFP

Metabolites known to occur in the cytosol of photosynthetic leaf cells were found to mediate the reversible conversion of pyrophosphate—D-fructose-6-phosphate 1-phosphotransferase (PFP) to phosphofructokinase (PFK) in partially purified preparations from spinach leaves. Preincubation of PFP with fructose 2,6-bisphosphate, ATP or fructose 6-phosphate converted PFP to PFK. The reverse reaction (PFK → PFP) was promoted by UDP-glucose plus pyrophosphate. These conversions in catalytic capability were accompanied by changes in molecular mass and charge. The results are in accord with the view that the alterations in PFP and PFK activity, provisionally called ‘metabolite-mediated catalyst conversion’, represent a regulatory mechanism to direct left cytosolic carbon flux in either the biosynthetic or degradatory direction