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Various other kinases act on small molecules such as lipids, carbohydrates, amino acids, and nucleotides, either for signaling or to prime them for metabolic pathways. Specific kinases are often named after their substrates. Protein kinases often have multiple substrates, and proteins can serve as substrates for more than one specific kinase.
Serine/threonine protein kinases (EC 2.7.11.1) phosphorylate the OH group of serine or threonine (which have similar side chains). Activity of these protein kinases can be regulated by specific events (e.g., DNA damage), as well as numerous chemical signals, including cAMP/cGMP, diacylglycerol, and Ca 2+ /calmodulin.
In eukaryotes, protein phosphorylation functions in cell signaling, gene expression, and differentiation. It is also involved in DNA replication during the cell cycle, and the mechanisms that cope with stress-induced replication blocks. Compared to eukaryotes, prokaryotes use Hanks-type kinases and phosphatases for signal transduction.
Eukaryotes initiate DNA replication at multiple points in the chromosome, so replication forks meet and terminate at many points in the chromosome. Because eukaryotes have linear chromosomes, DNA replication is unable to reach the very end of the chromosomes. Due to this problem, DNA is lost in each replication cycle from the end of the chromosome.
Like PARPs 2 and 3, the catalytic activity of PARP-1 is activated by discontinuous DNA fragments, DNA fragments with single-stranded breaks. PARP-1 binds histones near the axis where DNA enters and exits the nucleosome and additionally interacts with numerous chromatin-associated proteins which allow for indirect association with chromatin. [ 30 ]
ATP is involved in signal transduction by serving as substrate for kinases, enzymes that transfer phosphate groups. Kinases are the most common ATP-binding proteins. They share a small number of common folds. [31] Phosphorylation of a protein by a kinase can activate a cascade such as the mitogen-activated protein kinase cascade. [32]
Nucleoside-diphosphate kinases (NDPKs, also NDP kinase, (poly)nucleotide kinases and nucleoside diphosphokinases) are enzymes that catalyze the exchange of terminal phosphate between different nucleoside diphosphates (NDP) and triphosphates (NTP) in a reversible manner to produce nucleotide triphosphates. Many NDP serve as acceptor while NTP ...
During DNA replication, the replisome will unwind the parental duplex DNA into a two single-stranded DNA template replication fork in a 5' to 3' direction. The leading strand is the template strand that is being replicated in the same direction as the movement of the replication fork.