Nucleoprotein

Nucleoproteins or nucleopeptides are compounds consisting of a nucleic acid component and protein component (nucleoproteins) or peptide component. Relatively low-molecular-weight proteins or peptides are 

An important source of nucleoproteins is cell material, cytoplasm, from which, on centrifugation at various rates of acceleration (expressed in terms of gravitational acceleration g), nuclei (500-1000 ), mitochondria (10,000-15,000 ), and microsomes (20,000-100,000 ) can be obtained. 

Microsomes consist of a template of lipoproteins on which are arranged what are known as ribosomes. The lipoproteins and ribosomes themselves consist of two different classes of compounds always present in the same proportion by weight Lipoproteins are combinations of lipids and proteins, ribosomes are combinations of nucleic acid and proteins. On treating the microsomes with deoxycholic acid, the lipoproteins are freed and ribosomes are obtained. 

In ribosomes, the bonding of the protein to the nucleic acid occurs via Mg ions. Several ribosomes are joined to form what are known as polysomes. The bonding is affected by m-RNA (cf. Section 30.3.1). 

Fish sperm contain nucleoprotattiines. Upon treatment with sulfuric acid, the nucleoprotamines are reduced to nucleic acid and protamine sulfate. The chemically heterogeneous protamines of molecular weight 2000-8000 thus obtained contain only a few different kinds of amino acid residues per molecule. They are relatively rich in basic amino acids, as the composition of the protamines clupeine and salmine shows (Table 29-4), and never contain cystine, aspartic acid, or tryptophan. The basic amino acids are responsible for the bonding of the protein to the nucleic acid component. 

In general all animal and viral DNA and RNA (with the possible exception of tRNA) occur in vivo in more or less specific association with structural or functional proteins. For instance, the low-molecular weight basic histones (and sometimes the protamines) appear to be strongly and stoichiometrically com-plexed to the DNA in cells. Other superstructures with nucleic acids are built up by complexes with enzymes, repressors, ribosomal proteins, capsid proteins (capsomeres), etc. 

Boiko et al. [132] studied the effect of divalent cations on the stability of thymus deoxyribonucleoprotein. The degree of dissociation after gradient dialysis and reconstitution was assayed by gel chromatography. 

McCole et al. [133] elaborated a technique based on gel chromatography by which microsomal membranes can be rapidly and gently separated from free polyribosomes and soluble proteins. Lui and Ecobichon [134] used GPC for the isolation of microsomes from guinea pig liver. 

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A constituent of the nucleic acid portion of nucleoproteins, and, combined, as adenosine pyrophosphate, it plays an important part in many metabolic processes. 

Nucleoproieins. The prosthetic group of the nucleoproteins is nucleic acid, often linked through salt linkages with protamines or histones. The nucleoproteins are present in the nuclei of all cells. Chromasomes are largely nucleoproteins and some plant viruses and bacteriophages have been shown to be pure nucleoproteins. See also histones. 

Bustamente C, Keller D and Yang G 1993 Scanning force microscopy of nucleic acids and nucleoprotein assemblies Curr. Opin. Struct. Biol. 3 363... 

NUCLEOPROTEINS. Nucleoprotein conjugates have many roles in the storage and transmission of genetic information. Ribosomes are the sites of protein synthesis. Virus particles and even chromosomes are protein-nucleic acid complexes. 

The DNA in a eukaryotic cell nucleus during the interphase between cell divisions exists as a nucleoprotein complex called chromatin. The proteins of chromatin fall into two classes histones and nonhistone chromosomal proteins. 

Kem-eisen, n. mottled white pig iron (Elec.) core iron, -eiweisskorper, -eiweisstoff, m. nucleoprotein. -farbe,/., -f bemlttel, n., -farbstoff, m. nuclear stain, -f bung, /, Micros.) nuclear staining, -faser, /. nuclear fiber or filament. 

Baltimore D (1988) Gene therapy. Intracellular immunization. Nature 335 395-396 Basta S, Stoessel R, Easier M, van den Broek M, Groettrup M (2005) Cross-presentation of the long-lived lymphocytic choriomeningitis virus nucleoprotein does not require neosynthesis and is enhanced via heat shock proteins. J Immunol 175 796-805 Baum C (2007) Insertional mutagenesis in gene therapy and stem cell biology. Curr Opin Hematol 14 337-342... 

In terms of their molecular structures, the nucleotide and protein realms are usually considered to be rather independent of each other. However, these two families of molecules are covalently linked in the translational aminoacyl- RNAs and ribonucleoproteins as well as in the nucleoproteins involved in cellular and viral replication. In these hybrid biomolecules, a (deoxy)ribose phosphate moiety serves as the structural connection between the nucleoside and peptide moieties. 

A ribosome is a cytoplasmic nucleoprotein stmcture that acts as the machinery for the synthesis of proteins from the mRNA templates. On the ribosomes, the mRNA and tRNA molecules interact to translate into a specific protein molecule information transcribed from the gene. In active protein synthesis, many ribosomes are associated with an mRNA molecule in an assembly called the polysome. 

The packaging of nucleoproteins within chromatids is not random, as evidenced by the characteristic patterns observed when chromosomes are stained with specific dyes such as quinacrine or Giemsa s stain (Figure 36-6). 

From individual to individual within a single species, the pattern of staining (banding) of the entire chromosome complement is highly reproducible nonetheless, it differs significantly from other species, even those closely related. Thus, the packaging of the nucleoproteins in chromosomes of higher eukaryotes must in some way be dependent upon species-specific characteristics of the DNA molecules. 

In addition to its coenzyme role, NAD is the source of ADP-ribose for the ADP-ribosylation of proteins and polyADP-ribosylation of nucleoproteins involved in the DNA repair mechanism. 

A unique feature of such DNA-directed self-assemblies is their site-selective immobilization, which makes it possible to construct well-defined nanostructures. On the other hand, the possibility of the introduction of a vast number of substitutes (like peptidic sequences, nucleoproteins, of hydrophobic hydrocarbon chains) to an adamantane core (adamantyl) makes such a process capable of designing steric colloidal and supramolecular conformations by setting hydrophobic/hydrophilic and other interactions. In addition, the rigidity of the adamantane structure can provide strength and rigidity to such self-assemblies [150]. 

Telomeres are the nucleoprotein assembUes at the ends of chromosomes that comprise guanine-rich tandem-repeating DNA sequences (the size of a typical telomere is aroimd 6-12 kb in length in hiunans) together with a number of structural and regulatory proteins. The major function of telomeres is to protect chromosome ends from base-pair loss and end-to-end fusions, thereby safeguarding the integrity of each chromosome [10, llj. The enzyme... 

Scleroproteins, insoluble in most solvents. Localized in connective tissue, bone, hair, and skin. The two principal classes are the collagens and keratins Nucleoproteins, nucleic acid... 

The chromosome structure is visible only during the mitotic portion of the cell cycle. The constituent parts of the chromosomes are nucleoprotein fibers called chromatin. When condensed, chromatin forms a microscop-ically visible chromosome-like structure. The chromosomes are composed of DNA, RNA, and proteins. The relative amounts of the three vary, but chromatin is primarily protein and DNA. 

Kenner, R. A. and Aboderin, A. A. (1971). A new fluorescent probe for protein and nucleoprotein conformation. Binding of 7-(p-Methoxyben-zylamino) -4-nitrobenzoxadiazole to bovine trypsinogen and bacterial ribosomes. Biochemistry 10, 4433 1440. 

In addition to small organic molecules or metal ions, proteins may have other components tightly associated with them. Nucleoproteins, for instance, contain noncovalently bound DNA or RNA, as in some of the structural proteins of viruses. Lipoproteins contain associated lipids or fatty acids and may also carry cholesterol, as in the high-density and low-density lipoproteins in serum. 

Shetty, J.K., and Kinsella, J.E. (1980) Ready separation of proteins from nucleoprotein complexes by reversible modification of lysine residues. Biochem. J. 191, 269-272. 

Four processes are concerned in the isolation of a nucleic acid. First is the destruction of the tissue structure (stage 1). A nucleoprotein complex is then separated from other cellular constituents (stage 2). This complex is dissociated and the protein is removed (stage 3) and, finally, the nucleic acid is precipitated from the resulting solution (stage 4). Disintegration of... 

In a number of methods, isolation of the nucleoprotein complex (stage 2) is avoided. In the isolation of ribonucleic acid from beef pancreas,1241 nuclear material and cell debris are removed from a normal-saline extract of the minced tissue, which is then brought to half-saturation with sodium chloride (to dissociate the protein from the nucleic acid). After removal of the protein, the nucleic acid is precipitated with alcohol. However, the suggestion has been made126 that it is more satisfactory to isolate the nucleoprotein first, and this has been carried out, for instance, in the extraction of the ribonucleic acid from fowl sarcoma GRCH 15.126 Nucleoprotein complexes have also been isolated from baker s yeast127 and have been separated into various fractions, the nucleic acids from which differ slightly in composition. In addition, nucleoproteins have been isolated by complex formation with cetyltrimethylammonium bromide.128... 

In the past, dissociation of the nucleoprotein complex has been brought about by salt solutions or by heat denaturation,129 but, more recently, decomposition has been effected by hydrolysis with trypsin,126 or by the use of dodecyl sodium sulfate130 or strontium nitrate.131 Some virus nucleoproteins are decomposed by ethyl alcohol.132 This effect may be similar to that of alcohol on the ribonucleoproteins of mammalian tissues. If minced liver is denatured with alcohol, and the dried tissue powder is extracted with 10% sodium chloride, the ribonucleoproteins are decomposed to give a soluble sodium ribonucleate while the deoxyribonucleoproteins are unaffected.133 On the other hand, extraction with 10 % sodium chloride is not satisfactory unless the proteins have first been denatured with alcohol. Denaturation also serves to inactivate enzymes of the tissues which might otherwise bring about degradation of the nucleic acid during extraction. 

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