High Affinity Dimerization by Ski Involves Parallel Pairing of a Novel Bipartite α-Helical Domain
Year: 1997
Type: article
Abstract: c-Ski protein possesses a C-terminal dimerization domain that was deleted during the generation of v-ski, and has been implicated in the increased potency of c-ski in cellular transformation compared with the viral gene. The domain is predicted to consist of an extended alpha-helical segment made up of two motifs: a tandem repeat (TR) consisting of five imperfect repeats of 25 residues each and a leucine zipper (LZ) consisting of six heptad repeats. We have examined the structure and dimerization of TR or LZ individually or the entire TR-LZ domain. Using a quenched chemical cross-linking method, we show that the TR dimerizes with moderate efficiency (Kd = 4 x 10(-6) M), whereas LZ dimerizes poorly (Kd > 2 x 10(-5) M). However, the entire TR-LZ domain dimerizes efficiently (Kd = 2 x 10(-8) M), showing a cooperative effect of the two motifs. CD analyses indicate that all three proteins contain predominantly alpha-helices. Limited proteolysis of the TR-LZ dimer indicates that the two helical motifs are linked by a small loop. Interchain disulfide bond formation indicates that both the LZ and TR helices are oriented in parallel. We propose a model for the dimer interface in the TR region consisting of discontinuous clusters of hydrophobic residues forming "leucine buttons."
Source: Journal of Biological Chemistry
Authors: Guoxing Zheng, Kenneth M. Blumenthal, Yonggang Ji, Deborah L. Shardy, Steven B. Cohen, Edward Stavnezer
Institutions: Case Western Reserve University, University of Cincinnati
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W2085640419