The basis for K-Ras4B binding specificity to protein farnesyl-transferase revealed by 2 angstrom resolution ternary complex structures

Citation
Sb. Long et al., The basis for K-Ras4B binding specificity to protein farnesyl-transferase revealed by 2 angstrom resolution ternary complex structures, STRUCT F D, 8(2), 2000, pp. 209-222
Citations number
51
Categorie Soggetti
Biochemistry & Biophysics
Journal title
STRUCTURE WITH FOLDING & DESIGN
ISSN journal
09692126 → ACNP
Volume
8
Issue
2
Year of publication
2000
Pages
209 - 222
Database
ISI
SICI code
0969-2126(20000215)8:2<209:TBFKBS>2.0.ZU;2-X
Abstract
Background: The protein farnesyltransferase (FTase) catalyzes addition of t he hydrophobic farnesyl isoprenoid to a cysteine residue fourth from the: C terminus of several protein accepters that are essential for cellular sign al transduction such as Ras and Rho, This addition is necessary for the bio logical function of the modified proteins. The majority of Ras-related huma n cancers are associated with oncogenic variants of K-RasB, which is the hi ghest affinity natural,substrate of FTase, Inhibition of FTase causes regre ssion of Ras-mediated tumors in animal models. Results: We present four ternary complexes of rat FTase cc-crystallized wit h farnesyl diphosphate analogs and K-Ras4B peptide substrates, The Ca(1)a(2 )X portion of the peptide substrate binds in an extended conformation:in th e hydrophobic cavity of FTase and coordinates the active site zinc ion, The se complexes offer the first view of the polybasic region of the K-Ras4B pe ptide substrate, which confers the major enhancement of affinity of this su bstrate. The polybasic region forms a type I beta turn and binds along the rim of the hydrophobic cavity, Removal of the catalytically essential zinc ion results ina dramatically different peptide conformation in which the Ca (1)a(2)X motif adopts a beta turn. A-manganese ion binds to the diphosphate mimic of the farnesyl diphosphate analog. Conclusions: These ternary complexes provide new insight into the molecular basis of peptide substrate specificity, and further define the roles of zi nc and magnesium in the prenyltransferase reaction. Zinc is essential for p roductive Ca(1)a(2)X peptide binding, suggesting that the p-turn conformati on identified in previous nuclear magnetic resonance (NMR) studies reflects a state in which the cysteine is not coordinated to the zinc ion. The stru ctural information presented here should facilitate structure-based design and optimization of inhibitors of Ca(1)a(2)X protein prenyltransferases.