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Solution Structure of the Transmembrane Nogo‐B Receptor and Insight into its Topological Orientation by Small Angle X‐ray Scattering Analysis
Author(s) -
Holcomb Joshua,
Spellmon Nicholas,
Shang Weifeng,
Miao Quing,
Yang Zhe
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.603.9
Subject(s) - transmembrane domain , transmembrane protein , chemistry , topology (electrical circuits) , receptor , biophysics , biology , biochemistry , mathematics , combinatorics
The Nogo‐B Receptor (NgBR) is newly identified class I transmembrane receptor known for its role in binding Nogo‐B and promoting angiogenesis by chemotaxis in vivo . Most recently we discovered that NgBR shows binding specificity for the farnesylated oncoprotein Ras and facilitates Ras activation by its recruitment to the plasma membrane. To understand the potential mode of interaction with farnesylated Ras, we performed Small Angle X‐ray Scattering (SAXS) analysis of the NgBR construct 79–293 which includes the currently accepted cytosolic and transmembrane domains with a portion of the extracellular region. SAXS analysis reveals the radius of gyration ( R g ) for our NgBR construct to be 18.2 Å with a maximum end to end distance (D max ) of 61 Å. Ab initio modeling returns a globular molecular envelope with an estimated molecular weight of 23 kD closely correlated with the calculated molecular weight of our NgBR construct. These data indicate that our NgBR construct is well folded and exists as a globular domain in solution with no apparent intrinsic disordered regions. However, this result is conflicting with the currently accepted topological orientation of NgBR which would separate our NgBR construct into three distinct regions: extracellular, transmembrane and cytosolic domains. However, comparison of the molecular envelope structure of our NgBR construct with the structure of Undecaprenyl Pyrophosphate Synthase (UPPs) which shares similar sequence homology to NgBR, further supports our conclusion that the regions included in our construct are folded into a single globular domain, as the two structures are highly superimposed. This led us to propose the idea that NgBR may exist in more than one topological orientation and that the currently accepted transmembrane domain may internalize and contribute to the overall fold of NgBR cytosolically, thereby a complete binding site for farnesylated Ras. Altogether, our SAXS analysis provides the first molecular envelope structure of the Nogo‐B Receptor and provides evidence for a topological orientation of NgBR not previously identified. Support or Funding Information Detroit Cardiovascular Training Program, NIH: National Heart, Lung, and Blood Institute