Interaction Site of GTP Binding Gh (Transglutaminase II) with Phospholipase C

The results revealed that the ⌬K676 mutant coimmunoprecipitated phospholipase C as effectively as the wild type, whereas the ⌬L656 and ⌬E646 mutants failed to coimmunoprecipitate PLC, showing a similar level to that of the ␣1B-receptor alone

Ki-Chul Hwang; Caroline D. Gray; Natarajan Sivasubramanian; Mie-Jae Im

2002

Scholarcy highlights

  • The G␣h protein, transglutaminase II,1 is unique in that the enzyme exhibits two distinct enzyme activities, namely guanosine triphosphatase and TGase, with a signal transfer role
  • The GTPase function of G␣h differs from other TGases, coagulation factor XIIIa, keratinocyte, and epidermal transglutaminases
  • The isolated full-length hhG␣h cDNA was an exact match in the nucleotide and deduced amino acid sequences with the human endothelial TGase II
  • The Ca2ϩstimulated TGase activities of expressed hhG␣h and its truncated mutants were completely inhibited with Ͼ100 ␮M GTP, and the inhibitory potency of GTP was in the range of 20 –50 ␮M for all hhG␣h proteins, confirming that GTP is a negative regulator for the TGase of G␣h
  • The results revealed that the ⌬K676 mutant coimmunoprecipitated phospholipase C as effectively as the wild type, whereas the ⌬L656 and ⌬E646 mutants failed to coimmunoprecipitate PLC, showing a similar level to that of the ␣1B-receptor alone
  • The Gh7␣ antibody did not coimmunoprecipitate PLC but effectively coimmunoprecipitated the receptor. These findings clearly demonstrate that the C-terminal region of hhG␣h from Val665 to Lys672 is a critical site for interaction and stimulation of PLC
  • Three charged amino acids in this region, i.e. a hydrophilic interaction, probably play a critical role in the contact of hhG␣h with phospholipase C

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