. 2005 Feb;11(2):187–196. doi: 10.1261/rna.7950605

TABLE 1.

Rates (k_obs) for the minimal and extended hammerheads in divalent and monovalent cations

	k_obs (min⁻¹)
Cation^a	Minimal hammerhead	Extended hammerhead
0.01 mM Mg²⁺	<0.001^b	0.036
1 mM Mg²⁺	0.125^b	5.5
10 mM Mg²⁺	0.25^b	>6
0.01 mM Mn²⁺	~0.02^b	4.2
1 mM Mn²⁺	2.2^b	>6
10 mM Mn²⁺	5^b	>6
0.01 mM Co(NH₃)₆³⁺	<0.001^c	0.019
0.1 mM Co(NH₃)₆³⁺	<0.001^c	0.009
100 mM Co(NH₃)₆³⁺	0.0071^c	ND^d
1 M Na⁺	ND^d	0.13
4 M Li⁺	0.18^e	ND^d

Note: All extended hammerhead reactions were single-turnover with excess enzyme relative to substrate and were carried out in 5 mM HEPES (pH 7.0) at 20°C.

^aAll experiments with multivalent cations were performed in a background of 100 mM Na⁺ except the rate determined in 100 mM Co(NH₃)₆³⁺.

^bHunsicker and DeRose (2000).

^cCurtis and Bartel (2001).

^dExperiment not performed at that concentration of cation.

^eO’Rear et al. (2001).