The 20S catalytic core of the 26S proteasome has the shape of a barrel made of four rings which are composed of seven differentαsubunitsα_1-α_7 at two outer rings and seven differentβsubunitsβ_1-β_7 at two inner rings at which the catalytic sites locate. Three of theβsubunits contain proteolyses sites, which are sequestered in the hollow interior of the 20S particle. Substrates enter the 20S through a narrow channel formed by theβsubunits, whose N-termini, depending on their conformation, can either obstruct or allow substrate entry and thus function as a gate. This entry channel is narrow and only permits passage of unfolded, linearized polypeptides.

哺乳動物26S蛋白酶體是由一個20S催化顆粒(catalytic particle欧美刺激性大交在线视频黑白，CP)和兩個19S調(diào)節(jié)顆粒(regulatory particle欧美黄色性交一级大屏，RP)組成的ATP(adenosine-triphosphate国产一区在线视频免费观看，ATP)依賴性蛋白水解酶復(fù)合體欧美性爱网络。20S CP是26S蛋白酶體的催化核心www成年人视频，它是由4個圓環(huán)堆疊形成的桶狀復(fù)合物亚洲三级片啪啪，其中兩側(cè)外環(huán)每個環(huán)是由α_1-α_7亞基組成，兩個內(nèi)環(huán)每個環(huán)是由β_1-β_7亞基組成亚洲一区二区免费视频网站，4個環(huán)的中央形成一個狹窄的內(nèi)腔操操网人人摸人人摸。2個β內(nèi)環(huán)形成了20S CP的催化中心空腔，其內(nèi)壁為催化活性位點所在地欧美黄色免费在线观看；外側(cè)α環(huán)中心的孔道是底物到達(dá)催化中心空腔的通道人人夜色精品国产噜噜噜，一般被α亞基上的N末端所封閉，阻止胞內(nèi)非目的靶蛋白進入20S CP內(nèi)被降解破壞综合网图。