Ribonuclease function

Cirino NM, Cameron CE, Smith JS, Rausch JW, Roth MJ, Benkovic SJ, et al. Divalent cation modulation of the ribonuclease functions of human immunodeficiency vims reverse transcriptase. Biochemistry 1995 34 9936-9943. 

Rait VK, O Leary TJ, Mason JT. Modeling formalin fixatin and antigen retrieval with bovine pancreatic ribonuclease A I—structural and functional alterations. Lab. Invest. 2004 84 292-299. 

Many extracellular proteins like immunoglobulins, protein hormones, serum albumin, pepsin, trypsin, ribonuclease, and others contain one or more indigenous disulfide bonds. For functional and structural studies of proteins, it is often necessary to cleave these disulfide bridges. Disulfide bonds in proteins are commonly reduced with small, soluble mercaptans, such as DTT, TCEP, 2-mercaptoethanol, thioglycolic acid, cysteine, etc. High concentrations of mercaptans (molar excess of 20- to 1,000-fold) are usually required to drive the reduction to completion. 

Komiyama at al. have prepared two oligonuclear Zn(II) complexes (22 and 23) and tested their hydrolytic activity toward different diribonucleotides [45,46] (catalytic turnover was not demonstrated). The dimer and trimer structures of the active species were confirmed by measuring the hydrolytic activity as a function of Zn/L ratio, which show sharp maxima at the expected 2/1 and 3/1 ratios, respectively. The oligomer complexes have high ribonuclease activity (e.g. the hydrolysis of UpU is accelerated more than 4 and 5 orders of magnitude by 22 and 23, respectively), whereas the effect of the monomer complex 24 was not... 

Cytokine profiling has also been measured as a function of changes in cytokine mRNA expression using either reverse transcription polymerase chain reaction (RT-PCR) [87, 91-93] or ribonuclease protection assay (RPA) [94-97], Measurement of cytokine transcripts by RT-PCR revealed that prolonged exposure to TMA induced increased levels of IL-4 mRNA expression compared with treatment with DNCB [87,92-93]. However, expression of the type 1 cytokine IFN-y by DNCB-activated LNC was variable and failed to discriminate between contact and respiratory allergens [87,91,93). A similar profile was observed for freshly isolated tissue analyzed by RPA. This somewhat less... 

Since the rate constants of bimolecular diffusion-limited reactions in isotropic solution are proportional to T/ these data testify to the fact that the kt values are linearly dependent on the diffusion coefficient D in water, irrespective of whether the fluorophores are present on the surface of the macromolecule (human serum albumin, cobra neurotoxins, proteins A and B of the neurotoxic complex of venom) or are localized within the protein matrix (ribonuclease C2, azurin, L-asparaginase).1 36 1 The linear dependence of the functions l/Q and l/xF on x/t] indicates that the mobility of protein structures is correlated with the motions of solvent molecules, and this correlation results in similar mechanisms of quenching for both surface and interior sites of the macromolecule. 

Fig. 4A The mechanism of cleavage by ribonuclease A. Two imidazole residues function as general acid-base catalysts. B The single-metal-ion mechanism proposed for cleavage by the hammerhead ribozyme. One metal ion binds directly to the pro-Rp oxygen and functions as a general base catalyst. C The double-metal-ion mechanism proposed for cleavage by the hammerhead ribozyme. Two metal ions bind directly to the 2 -oxygen and the 5 -oxygen...

The essential—SH group in D-glyceraldehyde-3-phosphate dehydrogenase and the imidazol residues of the ribonuclease are also more reactive because of side-chain interactions in the active center. Such functional groups may have such extremely high reactivity that an equivalent amount of the reagent causes full inactivation of the enzyme. 

The first examples of mechanism must be divided into two principal classes the chemistry of enzymes that require coenzymes, and that of enzymes without cofactors. The first class includes the enzymes of amino-acid metabolism that use pyridoxal phosphate, the oxidation-reduction enzymes that require nicotinamide adenine dinucleotides for activity, and enzymes that require thiamin or biotin. The second class includes the serine esterases and peptidases, some enzymes of sugar metabolism, enzymes that function by way of enamines as intermediates, and ribonuclease. An understanding of the mechanisms for all of these was well underway, although not completed, before 1963. 

Breslow s P-cyclodextrine ribonuclease model system represents one of the best examples concerning the construction of small enzyme-like molecules [33]. Breslow functionalized the P-cyclodextrine with two imidazole moieties (Figure 10.1). Selectively, catechol cyclic phosphate carrying a 4-tert-butyl group (Figure 10.1a) binds into the cavity of the catalyst (Figure 10. lb) in water solution, and is then hydrolyzed by the... 

Milk contains several phosphatases, the principal ones being alkaline and acid phosphomonoesterases, which are of technological significance, and ribonuclease, which has no known function or significance in milk. The alkaline and acid phosphomonoesterases have been studied extensively (see Andrews (1993) for references). 

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