A brain‐specific γ subunit of G protein freed from the corresponding β subunit under non‐denaturing conditions

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Abstract
It has generally been accepted that the β and γ subunits of G proteins are tightly associated and can only be dissociated under denaturing conditions. However, one form of the γ subunit, free of the β subunit, was isolated under non‐denaturing conditions during the purification of βγ complexes from bovine brain. Amino acid sequence analysis revealed that the N‐terminus of this γ subunit was not blocked and its sequence was identical to that of a brain‐specific γ subunit, γ3. Among three forms of γ subunits observed in bovine brain (γ2, γ3 and γ7), γ3 was the only form that was not modified at the N‐terminus. Although the physiological significance of the free form of γ3 is not clear, these results suggest that N‐terminal modification of γ subunits may be important for interaction with β subunits.