5tsw
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HIGH RESOLUTION CRYSTAL STRUCTURE OF A HUMAN TNF-ALPHA MUTANT
OverviewOverview
A human tumor necrosis factor-alpha (TNF-alpha) mutant (M3S) with low, systemic toxicity in vivo was designed, and its structures in two, different crystal packings were determined crystallographically at 1.8 and, 2.15-A resolution, respectively, to explain altered biological activities, of the mutant. M3S contains four changes: a hydrophilic substitution of, L29S, two hydrophobic substitutions of S52I and Y56F, and a deletion of, the N-terminal seven amino acids that is disordered in the structure of, wild-type TNF-alpha. Compared with wild-type TNF-alpha, it exhibits 11-, and 71-fold lower binding affinities for the human TNF-R55 and TNF-R75, receptors, respectively, and in vitro cytotoxic effect and in vivo, systemic toxicity of M3S are 20 and 10 times lower, respectively. However, in a transplanted solid tumor mouse model, M3S suppresses tumor growth, more efficiently than wild-type TNF-alpha. M3S is highly resistant to, proteolysis by trypsin, and it exhibits increased thermal stability and a, prolonged half-life in vivo. The L29S mutation causes substantial, restructuring of the loop containing residues 29-36 into a rigid segment, as a consequence of induced formation of intra- and intersubunit, interactions, explaining the altered receptor binding affinity and thermal, stability. A mass spectrometric analysis identified major proteolytic, cleavage sites located on this loop, and thus the increased resistance of, M3S to the proteolysis is consistent with the increased rigidity of the, loop. The S52I and Y56F mutations do not induce a noticeable, conformational change. The side chain of Phe56 projects into a hydrophobic, cavity, while Ile52 is exposed to the bulk solvent. Ile52 should be, involved in hydrophobic interactions with the receptors, since a mutant, containing the same mutations as in M3S except for the L29S mutation, exhibits an increased receptor binding affinity. The low systemic toxicity, of M3S appears to be the effect of the reduced and selective binding, affinities for the TNF receptors, and the superior tumor-suppression of, M3S appears to be the effect of its weak but longer antitumoral activity, in vivo compared with wild-type TNF-alpha. It is also expected that the, 1.8-A resolution structure will serve as an accurate model for explaining, the structure-function relationship of wild-type TNF-alpha and many, TNF-alpha mutants reported previously and for the design of new TNF-alpha, mutants.
DiseaseDisease
Known diseases associated with this structure: Asthma, susceptibility to OMIM:[191160], Dementia, vascular, susceptibility to OMIM:[191160], Malaria, cerebral, susceptibility to OMIM:[191160], Migraine without aura, susceptibility to OMIM:[191160], Septic shock, susceptibility to OMIM:[191160]
About this StructureAbout this Structure
5TSW is a Single protein structure of sequence from Homo sapiens. This structure superseeds the now removed PDB entry 4TSW. Full crystallographic information is available from OCA.
ReferenceReference
High resolution crystal structure of a human tumor necrosis factor-alpha mutant with low systemic toxicity., Cha SS, Kim JS, Cho HS, Shin NK, Jeong W, Shin HC, Kim YJ, Hahn JH, Oh BH, J Biol Chem. 1998 Jan 23;273(4):2153-60. PMID:9442056
Page seeded by OCA on Mon Nov 12 23:52:20 2007