ジャーナル: J Mol Biol / 年: 2011 タイトル: Stepwise expansion of the bacteriophage ϕ6 procapsid: possible packaging intermediates. 著者: Daniel Nemecek / Naiqian Cheng / Jian Qiao / Leonard Mindich / Alasdair C Steven / J Bernard Heymann / 要旨: The initial assembly product of bacteriophage ϕ6, the procapsid, undergoes major structural transformation during the sequential packaging of its three segments of single-stranded RNA. The ...The initial assembly product of bacteriophage ϕ6, the procapsid, undergoes major structural transformation during the sequential packaging of its three segments of single-stranded RNA. The procapsid, a compact icosahedrally symmetric particle with deeply recessed vertices, expands to the spherical mature capsid, increasing the volume available to accommodate the genome by 2.5-fold. It has been proposed that expansion and packaging are linked, with each stage in expansion presenting a binding site for a particular RNA segment. To investigate procapsid transformability, we induced expansion by acidification, heating, and elevated salt concentration. Cryo-electron microscopy reconstructions after all three treatments yielded the same partially expanded particle. Analysis by cryo-electron tomography showed that all vertices of a given capsid were either in a compact or an expanded state, indicating a highly cooperative transition. To benchmark the mature capsid, we analyzed filled (in vivo packaged) capsids. When these particles were induced to release their RNA, they reverted to the same intermediate state as expanded procapsids (intermediate 1) or to a second, further expanded state (intermediate 2). This partial reversibility of expansion suggests that the mature spherical capsid conformation is obtained only when sufficient outward pressure is exerted by packaged RNA. The observation of two intermediates is consistent with the proposed three-step packaging process. The model is further supported by the observation that a mutant capable of packaging the second RNA segment without previously packaging the first segment has enhanced susceptibility for switching spontaneously from the procapsid to the first intermediate state.
ダウンロード / ファイル: emd_5356.map.gz / 形式: CCP4 / 大きさ: 65.5 MB / タイプ: IMAGE STORED AS FLOATING POINT NUMBER (4 BYTES)
注釈
This is expansion intermediate of the bacteriophage phi6 procapsid that was obtained by RNA release from already packaged capsids.
ボクセルのサイズ
X=Y=Z: 2.62792 Å
密度
表面レベル
By EMDB: 1.62 / ムービー #1: 1.5
最小 - 最大
-4.86563253 - 6.11769676
平均 (標準偏差)
0.0 (±1.0)
対称性
空間群: 1
詳細
EMDB XML:
マップ形状
Axis order
X
Y
Z
Origin
-130
-130
-130
サイズ
260
260
260
Spacing
260
260
260
セル
A=B=C: 683.25916 Å α=β=γ: 90.0 °
CCP4マップ ヘッダ情報:
mode
Image stored as Reals
Å/pix. X/Y/Z
2.6279192307692
2.6279192307692
2.6279192307692
M x/y/z
260
260
260
origin x/y/z
0.000
0.000
0.000
length x/y/z
683.259
683.259
683.259
α/β/γ
90.000
90.000
90.000
start NX/NY/NZ
-62
-62
-62
NX/NY/NZ
125
125
125
MAP C/R/S
1
2
3
start NC/NR/NS
-130
-130
-130
NC/NR/NS
260
260
260
D min/max/mean
-4.866
6.118
0.000
-
添付データ
-
試料の構成要素
-
全体 : Expansion Intermediate 2 of the P1247 Procapsid of Bacteriophage phi6
全体
名称: Expansion Intermediate 2 of the P1247 Procapsid of Bacteriophage phi6
要素
試料: Expansion Intermediate 2 of the P1247 Procapsid of Bacteriophage phi6
ウイルス: Bacteriophage phi6 (ファージ)
-
超分子 #1000: Expansion Intermediate 2 of the P1247 Procapsid of Bacteriophage phi6
超分子
名称: Expansion Intermediate 2 of the P1247 Procapsid of Bacteriophage phi6 タイプ: sample / ID: 1000 集合状態: Icosahedral shell of P1 dimers with P2, P4 and P7 subunits Number unique components: 4