Chen Z, Heierhorst J, Mann R J, Mitchelhill K I, Michell B J, Witters L A, Lynch G S, Kemp B E, Stapleton D
St. Vincent's Institute of Medical Research, St. Vincent's Hospital, 41 Victoria Parade, Fitzroy, Vic., Australia.
FEBS Lett. 1999 Oct 29;460(2):343-8. doi: 10.1016/s0014-5793(99)01371-x.
A heterotrimeric member of the AMP-activated protein kinase (AMPK) isoenzyme family was purified from rat skeletal muscle by immunoaffinity chromatography, consisting of an alpha2 catalytic and two non-catalytic subunits, beta2 and gamma1. The AMPK beta2 cDNA (271 amino acids (aa), molecular weight (MW)=30¿ omitted¿307, pI 6. 3) was cloned from skeletal muscle and found to share an overall identity of 70% with beta1 (270 aa, MW=30¿ omitted¿475, pI 6.0). In the liver AMPK beta1 subunit, Ser-182 is constitutively phosphorylated whereas in skeletal muscle beta2 isoform, we find that Ser-182 is only partially phosphorylated. In addition, the autophosphorylation sites Ser-24, Ser-25 found in the beta1 are replaced by Ala-Glu in the beta2 isoform. beta2 contains seven more Ser and one less Thr residues than beta1, raising the possibility of differential post-translational regulation. Immunoblot analysis further revealed that soleus muscle (slow twitch) contains exclusively beta1 associated with alpha2, whereas extensor digitorum longus muscle alpha2 (EDL, fast twitch) associates with beta2 as well as beta1. Sequence analysis revealed that glycogen synthase, a known AMPK substrate, co-immunoprecipitated with the AMPK alpha2beta2gamma1 complex.
通过免疫亲和色谱法从大鼠骨骼肌中纯化出AMP激活的蛋白激酶（AMPK）同工酶家族的一种异源三聚体成员，它由一个α2催化亚基和两个非催化亚基β2和γ1组成。从骨骼肌中克隆出AMPK β2 cDNA（271个氨基酸（aa），分子量（MW）=30（省略）307，pI 6.3），发现它与β1（270个aa，MW=30（省略）475，pI 6.0）的总体一致性为70%。在肝脏AMPK β1亚基中，Ser-182持续磷酸化，而在骨骼肌β2同工型中，我们发现Ser-182只是部分磷酸化。此外，在β1中发现的自磷酸化位点Ser-24、Ser-25在β2同工型中被Ala-Glu取代。β2比β1多七个Ser残基和少一个Thr残基，增加了翻译后差异调节的可能性。免疫印迹分析进一步显示，比目鱼肌（慢肌）只含有与α2相关的β1，而趾长伸肌（EDL，快肌）的α2与β2以及β1相关。序列分析显示，糖原合酶是一种已知的AMPK底物，与AMPK α2β2γ1复合物共免疫沉淀。
