Protamine nucleus

The presence of diamino acids in all proteins led Kossel to suppose that there was a protamine nucleus (t.e, of diamino acids) in all proteins the more recent work, especially that by Osborne and Clapp on the gliadins, where the diamino acids are present in such small amounts, though it supports the theory, yet suggests that proteins may exist in which it is not present, more especially if the view of Emil Fischer be taken that all the proteins we know, even the crystalline ones, are still mixtures of several proteins. The isolation of complexes containing only diamino acids from proteins, where they are combined together, will be the only proof of a protamine nucleus in a protein molecule. 

The first cell cycle of the mouse embryo differs in many respects from the second and the following cell cycles. It is characterized by a long Gl phase that starts after the penetration of the spermatozoon or artificial activation of the oocyte. During this period the chromatin of the oocyte completes the second meiotic division and forms the female pronucleus. At the same time, in the fertilized egg, the highly condensed chromatin of the sperm nucleus decondenses and sperm-specific proteins, protamines, are replaced by histones. After the initial sperm chromatin... 

It has been reported that the plasmid vector is unable to translocate to the nucleus unless complexed in the cytoplasm with nuclear proteins possessing NLS. NLS are short karyophilic peptides on proteins that bind to specific transporter molecules in the cytoplasm, mediating their passage through the pore complexes to the nucleus. Examples of these peptides will be given later in this section. DNA can also be presented to cells in culture as a complex with polycations such as polylysine, or basic proteins such as protamine, total histones or specific histone fractions (110), cationized albumin, and others. These molecules increase the transfection efficiency. In addition histone HI is identified as transfection-enhancing protein in cell culture (111). 

Correct answer = C. Protamine complexes with insulin to form an insoluble complex that is slowly absorbed. Insulin is not administered orally because it is destroyed by proteases in the Gl tract. Diet therapy and/or sulfonylureas are often effective without additional insulin In the therapy of Type II diabetics. Ketoacidosis is the most life-threatening consequence of Type I diabetics and requires adequate treatment with insuiin, not sulfonylureas. Insulin acts by binding to specific receptors in the cell membrane, not in the nucleus. 

A family of basic proteins associated with the chromatin in the nucleus of the cell. Protamines are characterized by a high content of arginine and replace histones in the process of spermiogenesis. See Lewis, S.D. and Ausid, J., Protamine-like proteins evidence for a novel chromatin structure, Biochem. Cell Biol. 80, 353-361,2002 Meistrich, M.L., Moha-patra, B., Shirley, C.R., and Zhao, M., Roles of transition nuclear proteins in spermiogenesis, Chromasoma 111, 483 88, 2003 Aoki,... 

Vegetable viruses are also nucleoproteins. Animal viruses also contain lipids. Viruses differ not only in their RNA and protein fractions, but also in their molar masses (Table 29-5). In viruses, a nucleus of nucleic acids (virion) is enclosed in a protein sheath (capside). The nucleic acid-protamines and the histones are also nucleoproteins. 

However, in eukaryotes transcription and translation are separated in space by the nuclear membrane. Most relevant evidence indicates that transcription proceeds inside the cell nucleus, whereas translation takes place in the cytoplasm. Even such nuclear proteins as histones and protamines are synthesized in the cytoplasm. Therefore RNA transport must take place between transcription and translation. 

Basic proteins a group of small proteins rich in arginine and lysine, and found in the cell nucleus (see Histones) and in sperm (see Protamines). They form complexes with nucleic acids. 

Nucleoprotein heteropolar complexes of nucleic acids (in particular, nuclear DNA) with basic, acid-soluble proteins (histones or protamines), and with acidic, base- or detergent-soluble non-histone chromatin proteins. N. occur mainly in the chromatin of the cell nucleus in its quiescent state, and in the chromosomes when the nucleus is active, i.e. dividing. Many viruses consist entirely of N., but N. are absent from bacteria. N. are concerned in DNA replication, and in the control of gene function during protein biosynthesis. 

Two main groups of basic proteins have been found in the cell nucleus protamines, which are present only in the sperm of fish and lower animals (a protaminelike protein, galline, has been found in rooster sperm), and histones, found in all somatic cells. Protamines are acid-extractable polypeptides with a molecular weight ranging between 4,000 and 10,000. Basic amino acids (particularly arginine) constitute the main amino acids in the protamine polypeptide chain in fact, one-... 

Nucleoproteins are difficult to extract from mammalian spermatozoa this is not surprising because the nucleus of mammalian spermatozoa is protected against mechanical damage by a special keratinous membrane. The nuclear protein, like keratin, is rich in sulfur, but it contains more arginine than regular keratin. Studies on disrupted bull sperm nuclei revealed that the arginine content of mammalian sperm is intermediate between that of protamine and that of histone. Whether protamines are in fact present in mammalian sperm is not known. Analysis of a protein hydrolysate obtained after extraction of bull sperm does, however, indicate that a basic protein, relatively rich in arginine, is present in mammalian sperm. 

At the terminal stage of spermatogenesis of salmon fish, nucleohistones are replaced by nucleoprotamine. Not much is known about the mechanisms by which one kind of basic polypeptide is replaced by another. What seems certain is that protamines are made in the cytoplasm and transferred to the nucleus before the displacement can take place. Prior to the exchange, both types of basic proteins, preformed histones and newly synthesized protamines, are phosphorylated. 

In the nudeus we find a whole series of conq>oimds. The nudear sap contains proteins not belonging to the histone or protamine families. In addition, we find in the nucleus either protamines or histones, depending on the cell, and also lipides (around 10%). 

Studies on these nucleoproteins were started in 1868 by Friedrich Miescher in an attempt to clarify the nature of the cell nucleus. He used materials consisting mainly of nuclei. First he found in the nuclei of pus cells nuclear protein fractions rich in phosphoric acid which he called nucleins (Miescher, 1870). Later he discovered in the sperm head of Rhine salmon a compound in which the nuclein was combined with a nitrogenous base in a salt-like linkage. The nuclein was a crude substance, later called nucleic acid. The nitrogenous base, obtained as the double salt of platinic chloride, was named protamine (Miescher, 1874, 1897). However, Miescher failed to observe the proteic nature of protamine , which thus remained unknown for about 20 years. 

The nuclear basic protein of bull spermatozoa is thus considered to be a new class of histone (Coelingh, 1971), rich in arginine (resembling protamines in this respect) and cystine. The nucleus of the bull spermatozoon, therefore, may consist of a network of identical histone molecules linked by disulfide bridges and associated with DNA. 

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