The kinase homology domain of retinal guanylyl cyclases 1 and 2 specifies the affinity and cooperativity of interaction with guanylyl cyclase activating protein-2

Biochemistry. 1998 Aug 11;37(32):11264-71. doi: 10.1021/bi9809674.


RetGC-1 and RetGC-2 are photoreceptor membrane guanylyl cyclases that are regulated by the Ca2+-binding protein, GCAP-2. We used a protease protection assay to localize regions of the intracellular domains of RetGCs important for the interaction with GCAP-2 and found that GCAP-2 reduces the access of trypsin to a site in the kinase homology domain (KHD) of RetGC-1. The protective effect of GCAP-2 is independent of Ca2+. We also found that RetGC-2 and GCAP-2 interact cooperatively with high affinity, but RetGC-1 and GCAP-2 interact noncooperatively with low affinity. By analyzing RetGC-1/RetGC-2 chimeras we demonstrated that the affinity and cooperativity of the interaction with GCAP-2 is dictated by the structure of the KHD. These findings suggest that GCAP-2 interacts constituitively with the KHDs of RetGC-1 and RetGC-2 and that cGMP synthesis is controlled by Ca2+-dependent conformational changes in the RetGC/GCAP complex.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Calcium-Binding Proteins / chemistry
  • Calcium-Binding Proteins / metabolism*
  • Cattle
  • Egtazic Acid / metabolism
  • Endopeptidases / metabolism
  • Guanylate Cyclase / chemistry
  • Guanylate Cyclase / genetics
  • Guanylate Cyclase / metabolism*
  • Guanylate Cyclase-Activating Proteins
  • Humans
  • Hydrolysis
  • Kinetics
  • Phosphotransferases / chemistry
  • Phosphotransferases / metabolism*
  • Protein Binding / genetics
  • Protein Structure, Tertiary
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / metabolism
  • Retina / enzymology*
  • Rod Cell Outer Segment / enzymology
  • Sequence Homology, Amino Acid*


  • Calcium-Binding Proteins
  • GUCA1A protein, human
  • GUCA1B protein, human
  • Guanylate Cyclase-Activating Proteins
  • Recombinant Fusion Proteins
  • Egtazic Acid
  • Phosphotransferases
  • Endopeptidases
  • Guanylate Cyclase