Crystal and solution structures of fragments of the human leucocyte common antigen-related protein

TY - JOUR

T1 - Crystal and solution structures of fragments of the human leucocyte common antigen-related protein

AU - Vilstrup, Joachim

AU - Simonsen, Amanda

AU - Birkefeldt, Thea

AU - Strandbygård, Dorthe

AU - Lyngsø, Jeppe

AU - Pedersen, Jan Skov

AU - Thirup, Søren

PY - 2020/5

Y1 - 2020/5

N2 - Leucocyte common antigen-related protein (LAR) is a post-synaptic type I transmembrane receptor protein that is important for neuronal functionality and is genetically coupled to neuronal disorders such as attention deficit hyperactivity disorder (ADHD). To understand the molecular function of LAR, structural and biochemical studies of protein fragments derived from the ectodomain of human LAR have been performed. The crystal structure of a fragment encompassing the first four FNIII domains (LARFN1-4) showed a characteristic L shape. SAXS data suggested limited flexibility within LARFN1-4, while rigid-body refinement of the SAXS data using the X-ray-derived atomic model showed a smaller angle between the domains defining the L shape compared with the crystal structure. The capabilities of the individual LAR fragments to interact with heparin was examined using microscale thermophoresis and heparin-affinity chromatography. The results showed that the three N-terminal immunoglobulin domains (LARIg1-3) and the four C-terminal FNIII domains (LARFN5-8) both bound heparin, while LARFN1-4 did not. The low-molecular-weight heparin drug Innohep induced a shift in hydrodynamic volume as assessed by size-exclusion chromatography of LARIg1-3 and LARFN5-8, while the chemically defined pentameric heparin drug Arixtra did not. Together, the presented results suggest the presence of an additional heparin-binding site in human LAR.

AB - Leucocyte common antigen-related protein (LAR) is a post-synaptic type I transmembrane receptor protein that is important for neuronal functionality and is genetically coupled to neuronal disorders such as attention deficit hyperactivity disorder (ADHD). To understand the molecular function of LAR, structural and biochemical studies of protein fragments derived from the ectodomain of human LAR have been performed. The crystal structure of a fragment encompassing the first four FNIII domains (LARFN1-4) showed a characteristic L shape. SAXS data suggested limited flexibility within LARFN1-4, while rigid-body refinement of the SAXS data using the X-ray-derived atomic model showed a smaller angle between the domains defining the L shape compared with the crystal structure. The capabilities of the individual LAR fragments to interact with heparin was examined using microscale thermophoresis and heparin-affinity chromatography. The results showed that the three N-terminal immunoglobulin domains (LARIg1-3) and the four C-terminal FNIII domains (LARFN5-8) both bound heparin, while LARFN1-4 did not. The low-molecular-weight heparin drug Innohep induced a shift in hydrodynamic volume as assessed by size-exclusion chromatography of LARIg1-3 and LARFN5-8, while the chemically defined pentameric heparin drug Arixtra did not. Together, the presented results suggest the presence of an additional heparin-binding site in human LAR.

KW - ectodomain

KW - heparin binding

KW - leucocyte common antigen-related protein

KW - protein tyrosine phosphatase receptor

KW - SAXS

KW - synaptogenesis

KW - X-ray crystallography

UR - http://www.scopus.com/inward/record.url?scp=85084277064&partnerID=8YFLogxK

U2 - 10.1107/S2059798320003885

DO - 10.1107/S2059798320003885

M3 - Journal article

C2 - 32355037

AN - SCOPUS:85084277064

SN - 2059-7983

VL - 76

SP - 406

EP - 417

JO - Acta crystallographica Section D: Structural biology

JF - Acta crystallographica Section D: Structural biology

ER -