Do plants contain g protein-coupled receptors?

Plant Physiol. 2014 Jan;164(1):287-307. doi: 10.1104/pp.113.228874. Epub 2013 Nov 18.

Abstract

Whether G protein-coupled receptors (GPCRs) exist in plants is a fundamental biological question. Interest in deorphanizing new GPCRs arises because of their importance in signaling. Within plants, this is controversial, as genome analysis has identified 56 putative GPCRs, including G protein-coupled receptor1 (GCR1), which is reportedly a remote homolog to class A, B, and E GPCRs. Of these, GCR2 is not a GPCR; more recently, it has been proposed that none are, not even GCR1. We have addressed this disparity between genome analysis and biological evidence through a structural bioinformatics study, involving fold recognition methods, from which only GCR1 emerges as a strong candidate. To further probe GCR1, we have developed a novel helix-alignment method, which has been benchmarked against the class A-class B-class F GPCR alignments. In addition, we have presented a mutually consistent set of alignments of GCR1 homologs to class A, class B, and class F GPCRs and shown that GCR1 is closer to class A and/or class B GPCRs than class A, class B, or class F GPCRs are to each other. To further probe GCR1, we have aligned transmembrane helix 3 of GCR1 to each of the six GPCR classes. Variability comparisons provide additional evidence that GCR1 homologs have the GPCR fold. From the alignments and a GCR1 comparative model, we have identified motifs that are common to GCR1, class A, B, and E GPCRs. We discuss the possibilities that emerge from this controversial evidence that GCR1 has a GPCR fold.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Arabidopsis Proteins / chemistry
  • Guanine Nucleotide Exchange Factors / chemistry
  • Models, Molecular
  • Molecular Sequence Data
  • Plant Proteins / chemistry*
  • Protein Conformation
  • Protein Folding
  • Receptors, G-Protein-Coupled / chemistry*
  • Sequence Alignment / methods
  • Sequence Homology, Amino Acid

Substances

  • Arabidopsis Proteins
  • GCR1 protein, Arabidopsis
  • Guanine Nucleotide Exchange Factors
  • Plant Proteins
  • Receptors, G-Protein-Coupled