Name 2 amino acids present in the basic protein of chromosome
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Two types of proteins, i.e., acidic and basic proteins are found associated with DNA in chromosome.
Protamines:
These are simple proteins of molecular weight less than 4000 Daltons. Rich in basic amino acid arginine, found in spermatozoa of some fish (salmon), snail, fowl, etc. They are helically rapped around DNA. Polypeptides of protamine consists of 28 amino acid residue (19 arginines, 8-9 non-basic amino acids).
Histones:
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Small basic proteins associated with DNA of eukaryotic cells. They are structural proteins of chromatin and act as gene repressors also. In a wide variety of plants and animals, the ratio of DNA: Histone =1:1. There are 5 types of Histones i.e., HI (H5), H2A, H2B, H3 and H4. Histones are rich in arginine and lysine (basic amino acids). They lack tryptophan. Histones are highly modified as well as conserved proteins; with very little difference in amino acid sequences. On the basis of arginine and lysine contents, they are divided into 3 groups.
(i) High lysine rich — HI
(ii) Lysine rich — H2A, H2B
(iii) Arginine rich – H3, H4
Histones tend to depress genetic activity. They make DNA. They are structurally important in packaging DNA molecules
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Protamines:
These are simple proteins of molecular weight less than 4000 Daltons. Rich in basic amino acid arginine, found in spermatozoa of some fish (salmon), snail, fowl, etc. They are helically rapped around DNA. Polypeptides of protamine consists of 28 amino acid residue (19 arginines, 8-9 non-basic amino acids).
Histones:
ADVERTISEMENTS:
Small basic proteins associated with DNA of eukaryotic cells. They are structural proteins of chromatin and act as gene repressors also. In a wide variety of plants and animals, the ratio of DNA: Histone =1:1. There are 5 types of Histones i.e., HI (H5), H2A, H2B, H3 and H4. Histones are rich in arginine and lysine (basic amino acids). They lack tryptophan. Histones are highly modified as well as conserved proteins; with very little difference in amino acid sequences. On the basis of arginine and lysine contents, they are divided into 3 groups.
(i) High lysine rich — HI
(ii) Lysine rich — H2A, H2B
(iii) Arginine rich – H3, H4
Histones tend to depress genetic activity. They make DNA. They are structurally important in packaging DNA molecules
Read more
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The major chemical components of the chromosome are DNA, RNA (nucleic acids), and proteins (histones and nonhistones).There is, in addition, calcium, which seems to be associated with the DNA (Barton, 1951, Mazia, 1954a). Calcium is important in binding sections of the chromosome together (Mazia, Steffensen, 1955).DNA, RNA and protein all contribute to the chromosomal mass .
Nucleic acids:These constitute mostly DNA being about 35% along with histone protein (These are basic proteins having amino acids such as arginine and lysine in their molecules.)
The residual protein (nonhistone proteins) is acidic in nature characterized by the preponderance of amino acids tryptophane and tyrosine.The important nonhistone proteins of chromosomes are phosphoproteins, DNA polymerase, RNA polymerase, DPN pyrophosphorylase and nucleoside triphosphatases. In addition to histone or protamines there is another type of protein called chromosomin by Stedman and Stedman (1943), and containing high tryptophane contents.Histone is found in practically all the types of nuclei that have been studied. Histone has arginine and lysine amino acids and little tryptophane or tyrosineProtamine has 90% arginine and no tyrosine or tryptophane. Histones are highly viscous complex of DNA and may be removed from the chromosome by NaCl (concentration of one mol/litre) and DNA-histone ratio of the removed complex is about 1.2: 1 to 1.6: 1.
The nonhistone or residual protein remains in the chromosome after DNA and histones have been removed. It contains more tryptophane than in histones. Residual protein (chromosin of Mirsky and Pollister, 1946) and chromosomin of Stedman and Stedman (1947) have been found in chromosome. The amount of DNA are the same in all the cells, regardless of size, but the total protein content is in direct proportion to cellular volume.
hope it helps! (^^)
Nucleic acids:These constitute mostly DNA being about 35% along with histone protein (These are basic proteins having amino acids such as arginine and lysine in their molecules.)
The residual protein (nonhistone proteins) is acidic in nature characterized by the preponderance of amino acids tryptophane and tyrosine.The important nonhistone proteins of chromosomes are phosphoproteins, DNA polymerase, RNA polymerase, DPN pyrophosphorylase and nucleoside triphosphatases. In addition to histone or protamines there is another type of protein called chromosomin by Stedman and Stedman (1943), and containing high tryptophane contents.Histone is found in practically all the types of nuclei that have been studied. Histone has arginine and lysine amino acids and little tryptophane or tyrosineProtamine has 90% arginine and no tyrosine or tryptophane. Histones are highly viscous complex of DNA and may be removed from the chromosome by NaCl (concentration of one mol/litre) and DNA-histone ratio of the removed complex is about 1.2: 1 to 1.6: 1.
The nonhistone or residual protein remains in the chromosome after DNA and histones have been removed. It contains more tryptophane than in histones. Residual protein (chromosin of Mirsky and Pollister, 1946) and chromosomin of Stedman and Stedman (1947) have been found in chromosome. The amount of DNA are the same in all the cells, regardless of size, but the total protein content is in direct proportion to cellular volume.
hope it helps! (^^)
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