Nucleoproteins

            Nucleoproteins are any proteins that are structurally associated with nucleic acids, either DNA or RNA. Typical nucleoproteines include ribosomes, nucleosomes, and viral nucleocapsid proteins.

Deoxyribonucleoproteins

            A deoxyribonucleoprotein (DNP) is a complex of DNA and protein. The prototypical examples are nucleosomes, complexes in which genomic DNA is wrapped around clusters of eight histone proteins in eukaryotic cell nuclei to form chromatin. Protamines replace histones during spermatogenesis.

Ribonucleoproteins

            A ribonucleoprotein (RNP) is a complex of RNA and protein. The enzyme telomerase, vault ribonucleoproteins, RNase P, hnRNP and small nuclear RNPs (snRNPs), and ribosomes are ribonucleoproteins. Ribosomes consist of one molecule of each of 50 or more ribosomal proteins along with three different molecules of RNA in prokaryotes or four in eukaryotes.

            Some viruses are simple ribonucleoproteins, containing only one molecule of RNA and a number of identical protein molecules. Others are ribonucleoprotein or deoxyribonucleoprotein complexes containing a number of different proteins, and exceptionally more nucleic acid molecules.

Functions-

            In eukaryotic cells, DNA is associated with about an equal mass of histone proteins in a highly condensed nucleoprotein complex called chromatin. Deoxyribonucleoproteins in this kind of complex interact to generate a multiprotein regulatory complex in which the intervening DNA is looped or wound. The deoxyribonucleoproteins participate in regulating DNA replication and transcription.

            The ribonucleoproteins play a role of protection. mRNAs never occur as free RNA molecules in the cell. They always associate with ribonucleoproteins and function as ribonucleoprotein complexes.

            In the same way, the genomes of negative-strand RNA viruses never exist as free RNA molecule. The ribonucleoproteins protect their genomes from RNase. Nucleoproteins are often the major antigens for viruses because they have strain-specific and group-specific antigenic determinants.

Structure-

            Through crystallographic methods, the specific spatial structure and biological functions of many nucleoproteins are understood. The structures of many viral nucleoproteins have been determined, including those of influenza, rabies, Ebola, Bunyamwera, Schmallenberg, Hazara, Crimean-Congo hemorrhagic fever and Lassa. Important techniques for detecting the structures of nucleoproteins include X-ray diffraction, nuclear magnetic resonance and cryo-electron microscopy.

Classification of nucleoprotein-

1.      Histones – These are very basic proteins, basic because they are enriched in the amino acids arginine and lysine to a level of about 24 mole present. arginine and lysine at physiological pH are cationic

and can interact electrostatically with amionic nucleic acids. thus, being basic, histones bind tightly to DNA which is an acid. there are 5 types of histones in the eukaryotic chromosomes, namely H1, H2A, H2B, H3 and H4

2.   Non-histones-about 50% non-histones of chromatin have been found to be structural proteins and include such proteins as actin, and α- and β-tubulins and myosin. They vital ingredients of the chromosome, functioning during chromosome condensation and in the movement of chromosomes during mitosis and meiosis. many of the remaining 50%of the non-histones include all the enzymes and that are involved in DNA replication, in transcription and in the regulation of transcription. These proteins are not a highly conserved among organisms, although they must carry out similar enzymatic activities. Apparently they are not as important as the histones in maintaining chromosomes integrity.