2A93

NMR SOLUTION STRUCTURE OF THE C-MYC-MAX HETERODIMERIC LEUCINE ZIPPER, 40 STRUCTURES

Summary for 2A93

• Entry DOI: 10.2210/pdb2a93/pdb
• Descriptor: C-MYC-MAX HETERODIMERIC LEUCINE ZIPPER (2 entities in total)
• Functional Keywords: leucine zippers, 2d nmr, solution structure, h-bonds, buried salt bridge
• Cellular location: Nucleus, nucleoplasm: P01106; Nucleus: P28574
• Total number of polymer chains: 2
• Total formula weight: 7619.71

Authors

Lavigne, P.,Crump, M.P.,Gagne, S.M.,Hodges, R.S.,Kay, C.M.,Sykes, B.D. (deposition date: 1998-06-09, release date: 1999-01-27, Last modification date: 2024-11-20)

Primary citation

Lavigne, P.,Crump, M.P.,Gagne, S.M.,Hodges, R.S.,Kay, C.M.,Sykes, B.D.
Insights into the mechanism of heterodimerization from the 1H-NMR solution structure of the c-Myc-Max heterodimeric leucine zipper.
J.Mol.Biol., 281:165-181, 1998

PubMed Abstract: The oncoprotein c-Myc (a member of the helix-loop-helix-leucine zipper (b-HLH-LZ) family of transcription factors) must heterodimerize with the b-HLH-LZ Max protein to bind DNA and activate transcription. It has been shown that the LZ domains of the c-Myc and Max proteins specifically form a heterodimeric LZ at 20 degreesC and neutral pH. This suggests that the LZ domains of the c-Myc and Max proteins are playing an important role in the heterodimerization of the corresponding gene products in vivo. Initially, to gain an insight into the energetics of heterodimerization, we studied the stability of N-terminal disulfide-linked versions of the c-Myc and Max homodimeric LZs and c-Myc-Max heterodimeric LZ by fitting the temperature-induced denaturation curves monitored by circular dichroism spectroscopy. The c-Myc LZ does not homodimerize (as previously reported) and the c-Myc-Max heterodimeric LZ is more stable than the Max homodimeric LZ at 20 degreesC and pH 7.0. In order to determine the critical interhelical interactions responsible for the molecular recognition between the c-Myc and Max LZs, the solution structure of the disulfide-linked c-Myc-Max heterodimeric LZ was solved by two-dimensional 1H-NMR techniques at 25 degreesC and pH 4.7. Both LZs are alpha-helical and the tertiary structure depicts the typical left-handed super-helical twist of a two-stranded parallel alpha-helical coiled-coil. A buried salt bridge involving a histidine on the Max LZ and two glutamate residues on the c-Myc LZ is observed at the interface of the heterodimeric LZ. A buried H-bond between an asparagine side-chain and a backbone carbonyl is also observed. Moreover, evidence for e-g interhelical salt bridges is reported. These specific interactions give insights into the preferential heterodimerization process of the two LZs. The low stabilities of the Max homodimeric LZ and the c-Myc-Max heterodimeric LZ as well as the specific interactions observed are discussed with regard to regulation of transcription in this family of transcription factors.

PubMed: 9680483
DOI: 10.1006/jmbi.1998.1914

Experimental method

SOLUTION NMR