1k5a
Crystal structure of human angiogenin double variant I119A/F120A
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OverviewOverview
Human angiogenin (Ang) is an RNase in the pancreatic RNase superfamily, that induces angiogenesis. Its catalytic activity is comparatively weak, but nonetheless critical for biological activity. The crystal structure of, Ang has shown that enzymatic potency is attenuated in part by the, obstructive positioning of Gln117 within the B(1) pyrimidine binding, pocket, and that the C-terminal segment of residues 117-123 must reorient, for Ang to bind and cleave RNA. The native closed conformation appears to, be stabilized by Gln117-Thr44 and Asp116-Ser118 hydrogen bonds, as well as, hydrophobic packing of Ile119 and Phe120. Consistent with this view, Q117G, D116H, and I119A/F120A variants are 4-30-fold more active than Ang., Here we have determined crystal structures for these variants to examine, the structural basis for the activity increases. In all three cases, the, C-terminal segment remains obstructive, demonstrating that none of the, residues that has been replaced is essential for maintaining the closed, conformation. The Q117G structure shows no changes other than the loss of, the side chain of residue 117, whereas those of D116H and I119A/F120A, reveal C-terminal perturbations beyond the replacement site, suggesting, that the native closed conformation has been destabilized. Thus, the, interactions of Gln117 seem to be less important than those of residues, 116, 119, and 120 for stabilization. In D116H, His116 does not replicate, either of the hydrogen bonds of Asp116 with Ser118 and instead forms a, water-mediated interaction with catalytic residue His114; residues 117-121, deviate significantly from their positions in Ang. In I119A/F120A, the, segment of residues 117-123 has become highly mobile and all of the, interactions thought to position Gln117 have been weakened or lost; the, space occupied by Phe120 in Ang is partially filled by Arg101, which has, moved several angstroms. A crystal structure was also determined for the, deletion mutant des(121-123), which has 10-fold reduced activity toward, large substrates. The structure is consistent with the earlier proposal, that residues 121-123 form part of a peripheral substrate binding subsite, but also raises the possibility that changes in the position of another, residue, Lys82, might be responsible for the decreased activity of this, variant.
DiseaseDisease
Known diseases associated with this structure: Amyotrophic lateral sclerosis, susceptibility to OMIM:[105850]
About this StructureAbout this Structure
1K5A is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.
ReferenceReference
Crystallographic studies on the role of the C-terminal segment of human angiogenin in defining enzymatic potency., Leonidas DD, Shapiro R, Subbarao GV, Russo A, Acharya KR, Biochemistry. 2002 Feb 26;41(8):2552-62. PMID:11851402
Page seeded by OCA on Mon Nov 12 17:47:31 2007