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KMID : 0620919980300020081
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Experimental & Molecular Medicine
1998 Volume.30 No. 2 p.81 ~ p.86
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A new member of α1-adrenoceptor-coupled Gαh (transglutaminase Ⅱ) family in pig heart: purification and characterization
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Kwang Jin Baek/Soon Moon Yoo
Hyun Sik Jeong/Kee Jung Han/Sung Hye Cho/Hee Sung Lee/Hye Young Yun/Nyoun Soo Kwon/Kwang Jin Baek
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Abstract
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We previously reported an identification of a 77-kDa GTP-binding protein that co-purified with the α 1-adrenoceptor following ternary complex formation. In the present paper, we report on the purification and characterization of this GTP-binding protein (termed G α h5) isolated from pig heart membranes. After solubilization of pig heart membranes with NaCl, G α h5 was purified by sequential chromatographies using DEAE-Cellulose, Q-Sepharose, and GTP-agarose columns. The protein displayed high-affinity GTP γ S binding which is Mg(2+)-dependent and saturable. The relative order of affinity of nucleotide binding by G α 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 α h5 demonstrated transglutaminase (TGase) activity that was blocked either by EGTA or GTP γ S. In support of these observations, the G α h5 was recognized by a specific antibody to G α h7 or TGase II, indicating a homology with G α h (TGase II) family. These results demonstrate that 77-kDa G α h5 from pig heart is an α 1-adrenoceptor-coupled G α h (TGase II) family which has species-specificity in molecular mass.
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KEYWORD
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α1-adrenoceptor, G-protein, Gαh, transglutaminase, heart,
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