Sandbox GGC15: Difference between revisions
No edit summary |
No edit summary |
||
| (4 intermediate revisions by the same user not shown) | |||
| Line 5: | Line 5: | ||
== Structure == | == Structure == | ||
'''Human topo 1 is composed of 765 amino acids <ref name="Redinbo" />. The enzyme consist of 4 regions which are the NH2-terminal, core, linker, and COOH-terminal domains<ref name="Redinbo" />. The NH2-terminal is approximately 210 residues long, it is highly charged, disordered, and contains few hydrophobic amino acids<ref name="Redinbo" />. The <scene name='78/781215/04_27_structure_cooh/1'>COOH-terminal</scene> domain is made up of residues 713 to 765 and contains the important amino | '''Human topo 1 is composed of 765 amino acids <ref name="Redinbo" />. The enzyme consist of 4 regions which are the NH2-terminal, core, linker, and COOH-terminal domains<ref name="Redinbo" />. The NH2-terminal is approximately 210 residues long, it is highly charged, disordered, and contains few hydrophobic amino acids<ref name="Redinbo" />. The <scene name='78/781215/04_27_structure_cooh/1'>COOH-terminal</scene> domain is made up of residues 713 to 765 and contains the important amino acid <scene name='78/781215/04_27_structure_cooh_with_k/1'>Tyrosine 723</scene><ref name="Redinbo"/>. The location of the active site is at this amino acid<ref name="Redinbo" />. Residues 636 to 712 form the <scene name='78/781215/04_27_structure_linker/1'>Linker domain</scene> and they contribute to the enzyme catalytic activity but are not required<ref name="Redinbo" />. The core is divided into 3 subdomains: <scene name='78/781215/04_27_structure_core_sd1/1'>Core Sudomain 1</scene>[215-232 & 320-433], <scene name='78/781215/04_27_structure_core_sd2/1'>Core Subdomain 2</scene>[233-319], and <scene name='78/781215/04_27_structure_core_sd3/1'>Core Subdomain 3</scene>[434-635]<ref name="Redinbo"/>. The <scene name='78/781215/04_27_structure_core_cooh/1'>core and the COOH-terminal domains</scene> are very important for the catalytic activity<ref name="Redinbo" />.''' | ||
[[Image:Color Key.jpg]] | [[Image:Color Key.jpg]] | ||
== Active Site & Mechanism Of Action== | == Active Site & Mechanism Of Action== | ||
| Line 13: | Line 13: | ||
'''The active site of Topo 1 is catalytic and it is the location where the nicking or cutting occurs<ref name="Redinbo" />. The nicking occurs from the trans-esterification of Tyr-723 at a DNA phophodiester bond forming a <scene name='78/781215/04_27_19_active_site_mech/1'>3'-phosphotyrosine covalent enzyme–DNA complex</scene> <ref name="Staker" />. After the DNA is relaxed, the covalent intermediate is reversed when the released 5'-OH of the broken strand reattacks the phosphotyrosine intermediate in a second transesterification reaction<ref name="Staker" />.''' | '''The active site of Topo 1 is catalytic and it is the location where the nicking or cutting occurs<ref name="Redinbo" />. The nicking occurs from the trans-esterification of Tyr-723 at a DNA phophodiester bond forming a <scene name='78/781215/04_27_19_active_site_mech/1'>3'-phosphotyrosine covalent enzyme–DNA complex</scene> <ref name="Staker" />. After the DNA is relaxed, the covalent intermediate is reversed when the released 5'-OH of the broken strand reattacks the phosphotyrosine intermediate in a second transesterification reaction<ref name="Staker" />.''' | ||
[[Image: | [[Image:Active_Site_3_PM.jpg]]<ref name ="Stewart">Stewart, L. (1998). A Model for the Mechanism of Human Topoisomerase I. Science, 279(5356), 1534–1541. https://doi.org/10.1126/science.279.5356.1534</ref> | ||
[[Image:DNA and Tyrosine.jpg]]<ref name="Stewart" /> | [[Image:DNA and Tyrosine.jpg]]<ref name="Stewart" /> | ||
| Line 20: | Line 20: | ||
== Relevance == | == Relevance == | ||
'''Many anticancer drugs target topo 1 enzymes. This enzyme is the target of camptothecin (CPT) family of anticancer drugs<ref name="Redinbo" />. These drugs work by increasing the duration of the nicked intermediate in the <scene name='78/781215/04_28_revelance_cpt_bind/1'>topo I</scene> reaction <ref name="Redinbo" />. The stabilized intermediates prevent transcription and replication to continue in the cancer cells<ref name="Redinbo" />. This eventually leads to DNA damage and cell death<ref name="Redinbo" />.''' | '''Many anticancer drugs target topo 1 enzymes. This enzyme is the target of camptothecin (CPT) family of anticancer drugs<ref name="Redinbo" />. These drugs work by increasing the duration of the nicked intermediate in the <scene name='78/781215/04_28_revelance_cpt_bind/1'>topo I</scene> reaction <ref name="Redinbo" />. CPT enhances DNA breakage at sites with a guanine base at the +1 position on the DNA strand that is being cut<ref name="Redinbo" />. This is immediately downstream of the site that is being cleaved<ref name="Redinbo" />. The stabilized intermediates prevent transcription and replication to continue in the cancer cells<ref name="Redinbo" />. This eventually leads to DNA damage and cell death<ref name="Redinbo" />.''' | ||
[[Image:CPT and Enzyme.jpg]] <ref name="Redinbo" /> | [[Image:CPT and Enzyme.jpg]] <ref name="Redinbo" /> | ||