Exp Mol Med.  1998 Jun;30(2):81-86.

A new member of alpha 1-adrenoceptor-coupled G alpha h (transglutaminase II) family in pig heart: purification and characterization

• Yoo SM
• Jeong HS
• Han KJ
• Cho SH
• Lee HS
• Yun HY
• Kwon NS
• Baek KJ

Abstract

We previously reported an identification of a 77-kDa GTP-binding protein that co-purified with the alpha 1-adrenoceptor following ternary complex formation. In the present paper, we report on the purification and characterization of this GTP-binding protein (termed G alpha h5) isolated from pig heart membranes. After solubilization of pig heart membranes with NaCl, G alpha h5 was purified by sequential chromatographies using DEAE-Cellulose, Q-Sepharose, and GTP-agarose columns. The protein displayed high-affinity GTP gamma S binding which is Mg(2+)-dependent and saturable. The relative order of affinity of nucleotide binding by G alpha h5 was GTP > GDP > ITP >> ATP > or = adenyl-5'-yl imidodiphosphate, which was similar to that observed for other heterotrimeric G-proteins involved in receptor signaling. Moreover, the G alpha h5 demonstrated transglutaminase (TGase) activity that was blocked either by EGTA or GTP gamma S. In support of these observations, the G alpha h5 was recognized by a specific antibody to G alpha h7 or TGase II, indicating a homology with G alpha h (TGase II) family. These results demonstrate that 77-kDa G alpha h5 from pig heart is an alpha 1-adrenoceptor-coupled G alpha h (TGase II) family which has species-specificity in molecular mass.

Keyword

alpha1-adrenoceptor; G-protein; G alpha h transglutaminase; heart

MeSH Terms

Animal
Binding Sites
Binding, Competitive
Cross Reactions
GTP-Binding Proteins/metabolism*
GTP-Binding Proteins/isolation & purification*
GTP-Binding Proteins/immunology
Guanosine 5'-O-(3-Thiotriphosphate)/metabolism
Molecular Weight
Myocardium/chemistry*
Protein-Glutamine gamma-Glutamyltransferase/metabolism
Receptors, Adrenergic, alpha-1/metabolism
Swine