Prosthetic group nucleoprotein

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. 

Nucleoproteins are simple basic proteins (protamines or histones) in salt combination with nucleic acids as the prosthetic group. They are the important constituents of nuclei and chromatin. 

What are nucleoproteins What is a prosthetic group Give an example. 

In addition to pure proteins, there are still several classes of what are known as conjugated proteins, that is, compounds of proteins with non-o-amino acids, i.e., with what are called prosthetic groups. Chromoproteins are such compounds of proteins with metals. Glycoproteins contain less than 4%, but mucoproteins more than 4%, polysaccharides. Compounds of proteins with lipids are called lipoproteins, those with nucleic acids nucleoproteins, and those with flavine derivatives flavoproteins. Hemoproteins are compounds of proteins and iron porphyrines. 

Some proteins also contain a non-peptide portion that is attached chemically to the polyamide chain. The non-peptide moieties are called prosthetic groups, and the proteins with such groups are called conjugated proteins. Examples are hemoglobin and myoglobin that crmsist of polypeptide portions with iron-porphyrin prosthetic groups attached. This particular prosthetic group, called heme, is illustrated in Fig. 8.2. There are also a number of proteins that are associated with a nucleic acid. They are known as nucleoproteins. 

The presence of non-protein prosthetic groups as in glycoproteins, phosphoproteins, lipoproteins, chromoproteins and nucleoproteins. 

Lastly, the complex proteins have been gathered into a separate classification. They are composed of a protein part and an additional, nonprotein, prosthetic group. It is rather difficult to maintain the distinction between proteins which adsorb metals and carbohydrates or incorporate them in small quantities, and proteins with a definite metal or carbohydrate component. The usual division of complex proteins comprises the following (1) metalloproteins, (2) phosphopro-teins, (3) lipoproteins, (4) nucleoproteins, (5) glycoproteins, and (6) chromoproteins. 

Such a heterogeneous combination of components is not always of biologic significance. For example, it is uncertain whether the protein in nucleoproteins possesses any specific functions. On the other hand, we are well aware of the role of both the protein component and the prosthetic group in many enzymes, (cf. Chapt. V and VI.)... 

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