title: Dispensability of the [4Fe-4S] cluster in novel homologues of adenine glycosylase MutY.
abstract: 7,8-Dihydro-8-deoxyguanine (8oG) is one of the most common oxidative lesions in DNA. DNA polymerases misincorporate an adenine across from this lesion. Thus, 8oG is a highly mutagenic lesion responsible for G:C→T:A transversions. MutY is an adenine glycosylase, part of the base excision repair pathway that removes adenines, when mispaired with 8oG or guanine. Its catalytic domain includes a [4Fe-4S] cluster motif coordinated by cysteinyl ligands. When this cluster is absent, MutY activity is depleted and several studies concluded that the [4Fe-4S] cluster motif is an indispensable component for DNA binding, substrate recognition and enzymatic activity. In the present study, we identified 46 MutY homologues that lack the canonical cysteinyl ligands, suggesting an absence of the [4Fe-4S] cluster. A phylogenetic analysis groups these novel MutYs into two different clades. One clade is exclusive of the order Lactobacillales and another clade has a mixed composition of anaerobic and microaerophilic bacteria and species from the protozoan genus Entamoeba. Structural modeling and sequence analysis suggests that the loss of the [4Fe-4S] cluster is compensated by a convergent solution in which bulky amino acids substitute the [4Fe-4S] cluster. We functionally characterized MutYs from Lactobacillus brevis and Entamoeba histolytica as representative members from each clade and found that both enzymes are active adenine glycosylases. Furthermore, chimeric glycosylases, in which the [4Fe-4S] cluster of Escherichia coli MutY is replaced by the corresponding amino acids of LbY and EhY, are also active. Our data indicates that the [4Fe-4S] cluster plays a structural role in MutYs and evidences the existence of alternative functional solutions in nature.
authors.affiliation: Laboratorio Nacional de Genómica para la Biodiversidad, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Irapuato, Guanajuato, México.
authors.forename: Carlos H
authors.initials: CH
authors.lastname: Trasviña-Arenas
authors.affiliation: Laboratorio Nacional de Genómica para la Biodiversidad, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Irapuato, Guanajuato, México.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Lopez-Castillo
authors.affiliation: Laboratorio Nacional de Genómica para la Biodiversidad, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Irapuato, Guanajuato, México.
authors.forename: Eugenia
authors.initials: E
authors.lastname: Sanchez-Sandoval
authors.affiliation: Laboratorio Nacional de Genómica para la Biodiversidad, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Irapuato, Guanajuato, México.
authors.forename: Luis G
authors.initials: LG
authors.lastname: Brieba
mesh_terms: D000595:Amino Acid Sequence; D045647:DNA Glycosylases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004748:Entamoeba histolytica / Q000201:enzymology; D004926:Escherichia coli / Q000201:enzymology; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D052196:Levilactobacillus brevis / Q000201:enzymology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment
chemical_list: D007506:Iron-Sulfur Proteins; D045647:DNA Glycosylases; C061738:mutY adenine glycosylase
keywords: DNA repair; [4Fe-4S] cluster; adenine glycosylase; domain rearrangement