2r9a
From Proteopedia
Crystal structure of human XLF
Structural highlights
Disease[NHEJ1_HUMAN] Defects in NHEJ1 are the cause of severe combined immunodeficiency due to NHEJ1 deficiency (NHEJ1-SCID) [MIM:611291]; also known as autosomal recessive T-cell-negative, B-cell-negative, NK cell-positive, severe combined immunodeficiency with microcephaly, growth retardation and sensitivity to ionizing radiation or NHEJ1 syndrome. SCID refers to a genetically and clinically heterogeneous group of rare congenital disorders characterized by impairment of both humoral and cell-mediated immunity, leukopenia and low or absent antibody levels. Patients with SCID present in infancy with recurrent, persistent infections by opportunistic organisms. The common characteristic of all types of SCID is absence of T-cell-mediated cellular immunity due to a defect in T-cell development. NHEJ1-SCID is characterized by a profound T- and B-lymphocytopenia associated with increased cellular sensitivity to ionizing radiation, microcephaly and growth retardation. Some patients may manifest SCID with sensitivity to ionizing radiation without microcephaly and mild growth retardation, probably due to hypomorphic NHEJ1 mutations.[1] [2] [3] [4] Note=A chromosomal aberration involving NHEJ1 is found in a patient with polymicrogyria. Translocation t(2;7)(q35;p22).[5] Function[NHEJ1_HUMAN] DNA repair protein involved in DNA nonhomologous end joining (NHEJ) required for double-strand break (DSB) repair and V(D)J recombination. May serve as a bridge between XRCC4 and the other NHEJ factors located at DNA ends, or may participate in reconfiguration of the end bound NHEJ factors to allow XRCC4 access to the DNA termini. It may act in concert with XRCC6/XRCC5 (Ku) to stimulate XRCC4-mediated joining of blunt ends and several types of mismatched ends that are noncomplementary or partially complementary.[6] [7] [8] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedDNA double-strand breaks represent one of the most severe forms of DNA damage in mammalian cells. One pathway for repairing these breaks occurs via nonhomologous end-joining (NHEJ) and depends on XRCC4, LigaseIV, and Cernunnos, also called XLF. Although XLF stimulates XRCC4/LigaseIV to ligate mismatched and noncohesive DNA ends, the mechanistic basis for this function remains unclear. Here we report the structure of a partially functional 224 residue N-terminal fragment of human XLF. Despite only weak sequence similarity, XLF(1-170) shares structural homology with XRCC4(1-159). However, unlike the highly extended 130 A helical domain observed in XRCC4, XLF adopts a more compact, folded helical C-terminal region involving two turns and a twist, wrapping back to the structurally conserved N terminus. Mutational analysis of XLF and XRCC4 reveals a potential interaction interface, suggesting a mechanism for how XLF stimulates the ligation of mismatched ends. Crystal structure of human XLF: a twist in nonhomologous DNA end-joining.,Andres SN, Modesti M, Tsai CJ, Chu G, Junop MS Mol Cell. 2007 Dec 28;28(6):1093-101. PMID:18158905[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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