10.1021\/ja510513z<\/a><\/p>\nAuthors:<\/h4>\n
Thomas U. Nick, Wankyu Lee, Simone Ko\u00dfmann, Frank Neese, JoAnne Stubbe, Marina Bennati<\/p>\n
Abstract:<\/h4>\n
Ribonucleotide reductases (RNRs) catalyze the conversion of ribonucleotides to deoxyribonucleotides in all organisms. In all Class Ia RNRs, initiation of nucleotide diphosphate (NDP) reduction requires a reversible oxidation over 35 \u00c5 by a tyrosyl radical (Y122\u2022, Escherichia coli) in subunit \u03b2 of a cysteine (C439) in the active site of subunit \u03b1. This radical transfer (RT) occurs by a specific pathway involving redox active tyrosines (Y122 \u21c6 Y356 in \u03b2 to Y731 \u21c6 Y730 \u21c6 C439 in \u03b1); each oxidation necessitates loss of a proton coupled to loss of an electron (PCET). To study these steps, 3-aminotyrosine was site-specifically incorporated in place of Y356-\u03b2, Y731- and Y730-\u03b1, and each protein was incubated with the appropriate second subunit \u03b2(\u03b1), CDP and effector ATP to trap an amino tyrosyl radical (NH2Y\u2022) in the active \u03b12\u03b22 complex. High-frequency (263 GHz) pulse electron paramagnetic resonance (EPR) of the NH2Y\u2022s reported the gx values with unprecedented resolution and revealed strong electrostatic effects caused by the protein environment. (2)H electron-nuclear double resonance (ENDOR) spectroscopy accompanied by quantum chemical calculations provided spectroscopic evidence for hydrogen bond interactions at the radical sites, i.e., two exchangeable H bonds to NH2Y730\u2022, one to NH2Y731\u2022 and none to NH2Y356\u2022. Similar experiments with double mutants \u03b1-NH2Y730\/C439A and \u03b1-NH2Y731\/Y730F allowed assignment of the H bonding partner(s) to a pathway residue(s) providing direct evidence for colinear PCET within \u03b1. The implications of these observations for the PCET process within \u03b1 and at the interface are discussed.<\/p>\n","protected":false},"excerpt":{"rendered":"
DOI: 10.1021\/ja510513z Authors: Thomas U. Nick, Wankyu Lee, Simone Ko\u00dfmann, Frank Neese, JoAnne Stubbe, Marina Bennati Abstract: Ribonucleotide reductases (RNRs) catalyze the conversion of ribonucleotides to deoxyribonucleotides in all organisms. In all Class Ia RNRs, initiation of nucleotide diphosphate (NDP) reduction requires a reversible oxidation over 35 \u00c5 by a tyrosyl radical (Y122\u2022, Escherichia coli) […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-608","post","type-post","status-publish","format-standard","hentry","category-freeze-quench"],"_links":{"self":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/posts\/608","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=608"}],"version-history":[{"count":0,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/posts\/608\/revisions"}],"wp:attachment":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=608"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=608"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=608"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}