Tag: Lysine

  • Structure of DNA repair protein XRCC4  aka X-ray repair cross-complementing protein 4

    XRCC4 protein is a TETRAMER that resembles the shape of a DUMBBELL containing two globular ends separated by a long, thin stalk. The tetramer is composed of two dimers, and each dimer is made up of two similar subunits. The first subunit (L) contains amino acid residues 1 – 203 and has a longer stalk than the second…

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  • Staphylokinase (SAK) aka staphylococcal fibrinolysin or MĂĽller’s factor

    Staphylokinase (SAK; also known as staphylococcal fibrinolysin or MĂĽller’s factor) is a protein produced by Staphylococcus aureus. It contains 136 amino acid residues and has a molecular mass of 15kDa. Synthesis of staphylokinase occurs in late exponential phase. It is similar to streptokinase. Fibrinolysin is an enzyme derived from plasma of bovine origin (plasmin) or extracted from cultures of certain bacteria. (more below) Staphylokinase is positively…

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  • Protein phosphorylation was first reported in 1906

    Protein phosphorylation is a reversible post-translational modification of proteins in which an amino acid residue is phosphorylated by a protein kinase by the addition of a covalently bound phosphate group. Phosphorylation alters the structural conformation of a protein, causing it to become activated, deactivated, or otherwise modifying its function. Approximately 13,000 human proteins have sites that are phosphorylated. The reverse reaction of phosphorylation is called dephosphorylation, and is catalyzed by…

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  • Histones

    In biology, histones are highly basic proteins abundant in lysine and arginine residues that are found in eukaryotic cell nuclei. They act as spools around which DNA winds to create structural units called nucleosomes.[1][2] Nucleosomes in turn are wrapped into 30-nanometer fibers that form tightly packed chromatin. Histones prevent DNA from becoming tangled and protect it from DNA damage. In addition, histones play important roles in gene regulation and DNA replication. Without histones, unwound DNA in chromosomes would be…

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  • Heterochromatin

    Heterochromatin is a tightly packed form of DNA or condensed DNA, which comes in multiple varieties. These varieties lie on a continuum between the two extremes of constitutive heterochromatin and facultative heterochromatin. Both play a role in the expression of genes. Because it is tightly packed, it was thought to be inaccessible to polymerases and therefore not transcribed; however, according to Volpe et…

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