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Structure of the human MLH1 N-terminus: implications for predisposition to Lynch syndrome.

Wu H, Zeng H, Lam R, Tempel W, Kerr ID, Min J - Acta Crystallogr F Struct Biol Commun (2015)

Bottom Line: Although genetic testing for these mutations is available, robust classification of variants requires strong clinical and functional support.Here, the first structure of the N-terminus of human MLH1, determined by X-ray crystallography, is described.The structure shares a high degree of similarity with previously determined prokaryotic MLH1 homologs; however, this structure affords a more accurate platform for the classification of MLH1 variants.

View Article: PubMed Central - HTML - PubMed

Affiliation: Structural Genomics Consortium, University of Toronto, 101 College Street, Toronto, ON M5G 1L7, Canada.

ABSTRACT
Mismatch repair prevents the accumulation of erroneous insertions/deletions and non-Watson-Crick base pairs in the genome. Pathogenic mutations in the MLH1 gene are associated with a predisposition to Lynch and Turcot's syndromes. Although genetic testing for these mutations is available, robust classification of variants requires strong clinical and functional support. Here, the first structure of the N-terminus of human MLH1, determined by X-ray crystallography, is described. The structure shares a high degree of similarity with previously determined prokaryotic MLH1 homologs; however, this structure affords a more accurate platform for the classification of MLH1 variants.

No MeSH data available.


Related in: MedlinePlus

Superimposition of hLN40 and E. coli LN40 (PDB entry 1b62). hLN40 is colored yellow, while the E. coli homolog is colored green. The ATPase and transducer domains are located to the right and left, respectively, of the short loop colored blue. Residues in the ATP-binding loop of hLN40 are colored magenta, while those in E. coli LN40 are colored pink (the loop in the latter is ordered owing to extensive crystal contacts). In hLN40, ADP is depicted in stick representation and Mg2+ is shown as a green sphere. Secondary-structure elements are labelled beginning at the N-­terminus, with the first helix being αA and the first β-strand being β1.
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fig1: Superimposition of hLN40 and E. coli LN40 (PDB entry 1b62). hLN40 is colored yellow, while the E. coli homolog is colored green. The ATPase and transducer domains are located to the right and left, respectively, of the short loop colored blue. Residues in the ATP-binding loop of hLN40 are colored magenta, while those in E. coli LN40 are colored pink (the loop in the latter is ordered owing to extensive crystal contacts). In hLN40, ADP is depicted in stick representation and Mg2+ is shown as a green sphere. Secondary-structure elements are labelled beginning at the N-­terminus, with the first helix being αA and the first β-strand being β1.

Mentions: Crystals of the hMLH1 NTD formed in space group P64 with one molecule in the asymmetric unit. The crystallized hMLH1 construct contained residues 1–340 of the full-length protein. The crystallographic model included amino-acid residues 3–85, 98–299 and 320–336. Atoms with little or no electron density were deemed to be disordered and were omitted from the final model. Also included were ADP, an Mg2+ ion, 35 water molecules and nine sites with electron densities that we failed to confidently interpret in terms of specific chemical features. These sites are designated ‘UNX’ in the coordinate file (unknown atoms or ions). A DALI search (Holm & Rosenström, 2010 ▸) identified the E. coli MutL NTD (LN40; Ban & Yang, 1998 ▸) as the closest structural homolog (Fig. 1 ▸). Superimposition of our structure with the E. coli MutL–Mg–ADP ternary complex (PDB entry 1b62) using CEAlign (Jia et al., 2004 ▸; Shindyalov & Bourne, 1998 ▸) matches 288 Cα positions with a root-mean-square deviation (r.m.s.d.) of 2.5 Å. Given the similarity to E. coli MutL NTD and to be consistent with the nomenclature established by Ban & Yang (1998 ▸), we designate our structure human LN40 (hLN40).


Structure of the human MLH1 N-terminus: implications for predisposition to Lynch syndrome.

Wu H, Zeng H, Lam R, Tempel W, Kerr ID, Min J - Acta Crystallogr F Struct Biol Commun (2015)

Superimposition of hLN40 and E. coli LN40 (PDB entry 1b62). hLN40 is colored yellow, while the E. coli homolog is colored green. The ATPase and transducer domains are located to the right and left, respectively, of the short loop colored blue. Residues in the ATP-binding loop of hLN40 are colored magenta, while those in E. coli LN40 are colored pink (the loop in the latter is ordered owing to extensive crystal contacts). In hLN40, ADP is depicted in stick representation and Mg2+ is shown as a green sphere. Secondary-structure elements are labelled beginning at the N-­terminus, with the first helix being αA and the first β-strand being β1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4528928&req=5

fig1: Superimposition of hLN40 and E. coli LN40 (PDB entry 1b62). hLN40 is colored yellow, while the E. coli homolog is colored green. The ATPase and transducer domains are located to the right and left, respectively, of the short loop colored blue. Residues in the ATP-binding loop of hLN40 are colored magenta, while those in E. coli LN40 are colored pink (the loop in the latter is ordered owing to extensive crystal contacts). In hLN40, ADP is depicted in stick representation and Mg2+ is shown as a green sphere. Secondary-structure elements are labelled beginning at the N-­terminus, with the first helix being αA and the first β-strand being β1.
Mentions: Crystals of the hMLH1 NTD formed in space group P64 with one molecule in the asymmetric unit. The crystallized hMLH1 construct contained residues 1–340 of the full-length protein. The crystallographic model included amino-acid residues 3–85, 98–299 and 320–336. Atoms with little or no electron density were deemed to be disordered and were omitted from the final model. Also included were ADP, an Mg2+ ion, 35 water molecules and nine sites with electron densities that we failed to confidently interpret in terms of specific chemical features. These sites are designated ‘UNX’ in the coordinate file (unknown atoms or ions). A DALI search (Holm & Rosenström, 2010 ▸) identified the E. coli MutL NTD (LN40; Ban & Yang, 1998 ▸) as the closest structural homolog (Fig. 1 ▸). Superimposition of our structure with the E. coli MutL–Mg–ADP ternary complex (PDB entry 1b62) using CEAlign (Jia et al., 2004 ▸; Shindyalov & Bourne, 1998 ▸) matches 288 Cα positions with a root-mean-square deviation (r.m.s.d.) of 2.5 Å. Given the similarity to E. coli MutL NTD and to be consistent with the nomenclature established by Ban & Yang (1998 ▸), we designate our structure human LN40 (hLN40).

Bottom Line: Although genetic testing for these mutations is available, robust classification of variants requires strong clinical and functional support.Here, the first structure of the N-terminus of human MLH1, determined by X-ray crystallography, is described.The structure shares a high degree of similarity with previously determined prokaryotic MLH1 homologs; however, this structure affords a more accurate platform for the classification of MLH1 variants.

View Article: PubMed Central - HTML - PubMed

Affiliation: Structural Genomics Consortium, University of Toronto, 101 College Street, Toronto, ON M5G 1L7, Canada.

ABSTRACT
Mismatch repair prevents the accumulation of erroneous insertions/deletions and non-Watson-Crick base pairs in the genome. Pathogenic mutations in the MLH1 gene are associated with a predisposition to Lynch and Turcot's syndromes. Although genetic testing for these mutations is available, robust classification of variants requires strong clinical and functional support. Here, the first structure of the N-terminus of human MLH1, determined by X-ray crystallography, is described. The structure shares a high degree of similarity with previously determined prokaryotic MLH1 homologs; however, this structure affords a more accurate platform for the classification of MLH1 variants.

No MeSH data available.


Related in: MedlinePlus