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Solution structures, dynamics, and lipid‐binding of the sterile α‐motif domain of the deleted in liver cancer 2
Author(s) -
Li Hongyan,
Fung KingLeung,
Jin DongYan,
Chung Stephen SM,
Ching YickPang,
Ng Irene Oilin,
Sze KongHung,
Ko Ben C.B.,
Sun Hongzhe
Publication year - 2007
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.21361
Subject(s) - crystallography , circular dichroism , chemistry , biophysics , biology
Abstract The deleted in liver cancer 2 ( DLC2 ) is a tumor suppressor gene, frequently found to be underexpressed in hepatocellular carcinoma. DLC2 is a multidomain protein containing a sterile α‐motif (SAM) domain, a GTPase‐activating protein (GAP) domain, and a lipid‐binding StAR‐related lipid‐transfer (START) domain. The SAM domain of DLC2, DLC2‐SAM, exhibits a low level of sequence homology (15–30%) with other SAM domains, and appears to be the prototype of a new subfamily of SAM domains found in DLC2‐related proteins. In the present study, we have determined the three‐dimensional solution structure of DLC2‐SAM using NMR methods together with molecular dynamics simulated annealing. In addition, we performed a backbone dynamics study. The DLC2‐SAM packed as a unique four α‐helical bundle stabilized by interhelix hydrophobic interactions. The arrangement of the four helices is distinct from all other known SAM domains. In contrast to some members of the SAM domain family which form either dimers or oligomers, both biochemical analyses and rotational correlation time (τ c ) measured by backbone 15 N relaxation experiments indicated that DLC2‐SAM exists as a monomer in solution. The interaction of DLC2‐SAM domain with sodium dodecyl sulfate (SDS) micelles and 1,2‐dimyristoyl‐ sn ‐glycerol‐3‐phosphatidylglycerol (DMPG) phospholipids was examined by CD and NMR spectroscopic techniques. The DLC2‐SAM exhibits membrane binding properties accompanied by minor loss of the secondary structure of the protein. Deletion studies showed that the self‐association of DLC2 in vivo does not require SAM domain, instead, a protein domain consisting of residues 120–672 mediates the self‐association of DLC2. Proteins 2007. © 2007 Wiley‐Liss, Inc.