The formation of translational inhibitor (active eIF-2 kinase) from proinhibitor (inactive eIF-2 kinase) in reticulocyte lysates, known to be controlled by hemin, can, as we recently reported, be induced by 3':5'-cyclic AMP(cAMP)-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) or its catalytic subunit. We find that in crude preparations from rabbit reticulocyte lysates, h...

Archaeal replicative DNA polymerase D (PolD) constitute an atypical class of DNA polymerases made of a proofreading exonuclease subunit (DP1) and a larger polymerase catalytic subunit (DP2), both with unknown structures. We have determined the crystal structures of Pyrococcus abyssi DP1 and DP2 at 2.5 and 2.2 Å resolution, respectively, revealing a catalytic core strikingly different from all o...

Cyclic AMP activates protein kinase A by binding to an inhibitory regulatory (R) subunit and releasing inhibition of the catalytic (C) subunit. Even though crystal structures of regulatory and catalytic subunits have been solved, the precise molecular mechanism by which cyclic AMP activates the kinase remains unknown. The dynamic properties of the cAMP binding domain in the absence of cAMP or C...

diphtheria is a fatal disease caused by exotoxin of corynebacterium     diphtheria .  this toxin consists of   two chains, catalytic chain (a) and binding (b) chain. by binding chain (b),   the toxin binds to its receptor on numerous body cells such as myocardial,   kidney and peripheral nerve cells. after entering, catalytic chain (a)   inhibits protein synthesis and finally can cause cell dea...

15 Ribonucleotide reductases (RNRs) are key enzymes in DNA synthesis and repair, with 16 sophisticated allosteric mechanisms controlling both substrate specificity and overall activity. 17 In RNRs, the activity master-switch, the ATP-cone, has been found exclusively in the 18 catalytic subunit. In two class I RNR subclasses whose catalytic subunit lacks the ATP-cone, 19 we discovered ATP-cones ...

15 Ribonucleotide reductases (RNRs) are key enzymes in DNA synthesis and repair, with 16 sophisticated allosteric mechanisms controlling both substrate specificity and overall activity. 17 In RNRs, the activity master-switch, the ATP-cone, has been found exclusively in the 18 catalytic subunit. In two class I RNR subclasses whose catalytic subunit lacks the ATP-cone, 19 we discovered ATP-cones ...

Although Harderian glands are especially large in rodents, many features of this retroocular gland, including its development and function, are not well established. Protein phosphatase 2A (PP2A) is a family of heterotrimeric enzymes expressed in this gland. PP2A substrate specificity is determined by regulatory subunits with leucine 309 of the catalytic subunit playing a crucial role in the re...

The Snf1 kinase and its mammalian orthologue, the AMP-activated protein kinase (AMPK), function as heterotrimers composed of a catalytic alpha-subunit and two non-catalytic subunits, beta and gamma. The beta-subunit is thought to hold the complex together and control subcellular localization whereas the gamma-subunit plays a regulatory role by binding to and blocking the function of an auto-inh...

Acetohydroxyacid synthase (AHAS, EC 4.1.3.18) catalyzes the first step in the biosynthesis of the branched-chain amino acids. In bacteria, the enzyme has a large subunit containing the catalytic machinery and a small subunit with a regulatory role. In eucaryotes, the evidence for a regulatory subunit is largely indirect and circumstantial. We investigated the possibility that the yeast open rea...

Adenosine 3':5' -monophosphate (cyclic AMP) -dependent protein kinase from bovine heart muscle catalyzes the phosphorylation of its regulatory, cyclic AMP-binding subunit. Phosphorylation enhances net dissociation of the enzyme by cyclic AMP. Chromatography on omega-aminohexyl-agarose was used to study the effects of phosphorylation on cyclic AMP binding and subunit dissociation and reassociati...