Table 1.

Molecular architecture, fibrillization kinetics, and chemical stability of HET-s(218–289) mutants

Mutation	Mutation type	Abbreviation	9.4-Å meridional	Equatorial CC	Architecture	Lag time, min	kapp, min−1	m1/2, M
Wild-type	—	WT	Yes	1.00	β-Solenoid	21.8 ± 0.6	0.103 ± 0.002	2.77 ± 0.03
Reversed loop	Loop	RL	No	0.63	Stacked β-sheet	—	—	—
Scrambled loop	Loop	SL	No	0.66	Stacked β-sheet	—	—	—
Δ251–253	Loop	Δ251–253	Yes	0.96	β-Solenoid	147 ± 2	0.071 ± 0.004	2.30 ± 0.1
T233A	Buried polar	PA	Yes	0.91	β-Solenoid	23.0 ± 1	0.133 ± 0.007	2.94 ± 0.02
S273A	Buried polar	PB	Yes	0.83	β-Solenoid	77.0 ± 2	0.103 ± 0.007	1.98 ± 0.02
T233A-S273A	Buried polar	PAB	Yes	0.99	β-Solenoid	38.0 ± 2	0.098 ± 0.005	2.73 ± 0.06
E234A	Salt bridge	SA−	Yes	0.99	β-Solenoid	28.3 ± 0.9	0.151 ± 0.006	2.76 ± 0.03
E265A	Salt bridge	SB−	Yes	0.94	β-Solenoid	35.0 ± 2	0.120 ± 0.009	2.53 ± 0.02
E272A	Salt bridge	SC−	Yes	0.99	β-Solenoid	94.0 ± 2	0.106 ± 0.005	3.40 ± 0.2
E234A, E265A, E272A	Salt bridge	SABC−	Yes	0.98	β-Solenoid	219 ± 3	0.051 ± 0.003	2.27 ± 0.06
K229A	Salt bridge	SB+	Yes	0.90	β-Solenoid	66.0 ± 1	0.138 ± 0.006	3.20 ± 0.1
K270A	Salt bridge	SA+	Yes	0.98	β-Solenoid	30.0 ± 1	0.170 ± 0.01	2.63 ± 0.06
R236A	Salt bridge	SC+	Yes	0.99	β-Solenoid	59.0 ± 1	0.134 ± 0.007	2.78 ± 0.07
K229, K270A, R236A	Salt bridge	SABC+	Yes	—	β-Solenoid	111 ± 2	0.078 ± 0.003	1.94 ± 0.08
N226A	N ladder	NA	Yes	0.94	β-Solenoid	95.0 ± 3	0.087 ± 0.006	1.30 ± 0.2
N243A	N ladder	NB	Yes	0.96	β-Solenoid	91.0 ± 2	0.093 ± 0.005	1.84 ± 0.05
N262A	N ladder	NC	Yes	0.89	β-Solenoid	124 ± 4	0.068 ± 0.005	1.40 ± 0.2
N279A	N ladder	ND	Yes	0.90	β-Solenoid	121 ± 2	0.066 ± 0.003	2.39 ± 0.08
N226A, N243A	N ladder	NAB	Yes	0.84	β-Solenoid	139 ± 6	0.054 ± 0.006	0.470 ± 0.05
N226A, N279A	N ladder	NAD	Yes	—	β-Solenoid	97.0 ± 6	0.070 ± 0.01	0.250 ± 0.02
N243A, N262A	N ladder	NBC	Yes	—	β-Solenoid	311 ± 4	0.039 ± 0.002	0.700 ± 0.04
N262A, N279A	N ladder	NCD	Yes	0.84	β-Solenoid	298 ± 1	0.048 ± 0.003	1.28 ± 0.03
E234A, E265A, E272A, N226A, N243A	Salt bridge, N ladder	SN−	No	—	Stacked β-sheet	—	—	—
K229A, K270A, R236A, N262A, N279A	Salt bridge, N ladder	SN+	No	—	Stacked β-sheet	—	—	—

Mutation type refers to the type of structure affected by the mutation. Presence of the 9.4-Å meridional reflection indicates a two-rung structure. Equatorial CC is the correlation coefficient between WT and mutant equators; mutants with no listed CC were too disordered to perform quantitative analysis, so qualitative comparisons are shown in Table S1. Lag time is an empirical parameter representing time before exponential growth and k_app is an empirically calculated apparent first-order rate constant. Lag time and k_app for NAB and NAD are for the second aggregation step. m_1/2 is the guanidine concentration at the half-denaturation point.