RubisCO-like protein

Recall Why is rubisco likely to be the most abundant protein in nature ... 

Physical or chemical modification of a substrate may additionally selectively affect transformation or uptake Keil and Kirchman (1992) compared the degradation of Rubisco uniformly labeled with 3H amino acids produced via in vitro translation to Rubisco that was reductively methylated with 3H-methane. Although both Rubisco preparations were hydrolyzed to lower molecular weights at approximately the same rate, little of the methylated protein was assimilated or respired. The presence of one substrate may also inhibit uptake of another, as has been demonstrated for anaerobic rumen bacteria. Transport and metabolism of the monosaccharides xylose and arabinose were strongly reduced in Ruminococcus albus in the presence of cellobiose (a disaccharide of glucose), likely because of repression of pentose utilization in the presence of the disaccharide. Glucose, in contrast, competitively inhibited xylose transport and showed noncompetitive inhibition of arabinose transport, likely because of inactivation of arabinose permease (Thurston et al., 1994). 

Figure 3-2. Crystals of various proteins from the hyperthermophilic archaeon, Thermococcus kodakaraensis KOD1. A, rod-like crystal of 06-methylguanine-DNA methyltransferase (MGMT) B, plate-like crystal of MGMT C, bar-like crystal of DNA polymerase D, cubic or hexagonal crystals of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco).

The aggregated structure of the mutant was further solved by electron microscopic analysis. The images of negatively stained samples indicate that the mutant molecules have a ring like structure, similar to that previously reported for LgSg Rubisco (Fig.3). A four fold radial symmetry was deduced from rotational analysis. All these data strongly suggest an L8 type for the mutant protein. 

Potential targets should also be present at low intracellular concentrations so that inhibitors will be more likely to have lower use rates and reduced environmental impact. Ribulose-l,5>bisphosphate carboxylase/oxygenase (Rubisco) serves as a negative example of this point While it plays a key role in plant specific metabolism, it is far too abundant to inhibit in a practical sense. Rubisco is thought to comprise up to 50% of the soluble leaf protein (7) and we estimate that even an ideal inhibitor, one that completely inhibits all of the enzyme in a 1 1 ratio of inhibitor to enzyme, would require a use rate of approximately SO kg/ha to completely tie up all iht enz e molecules. Lethal effects would probably be observed with less than 100% inhibition, but the use rates would still be impractical. 

Spinach chloroplast envelope membranes, incubated in vitro in the presence of [y PJATP, incorporated labelled phosphate mainly in three proteins exhibiting Mr of 67, 26 and 14 kDa. Two of them, the 26 and 14 kDa phosphoproteins, are pools of LHCIIb and Rubisco small subunit tightly bound to envelope membranes [1] and are phosphorylated by a unique Ca -dependent serine protein kinase [2]. The 67 kDa phosphoprotein is likely to be autophosphorylated its P-labelling would take place via its own phosphoglucomutase activity [2-4]. The aim of this investigation is to modulate envelope protein kinase activities following incubation for various times with the phospholipase C (PLC) from Bacillus cereus or the lipase from Rhizopus arrhizus (LRa). 

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