Lysin
This is a project in collaboration with and David Stout at TSRI.
41. Diller T.C., Shaw A, Stura E.A., Vacquier V.D., Stout C.D. (1994) Acid pH crystallization of the basic protein
lysin from the spermatozoa of red abalone (Haliotis rufescens).
Acta Cryst. D50 : 620-626.
Abstract: A new crystal form of dimeric red lysin, a distinctly basic protein (Mr = 16070) from the red abalone (Haliotis rufescens), has been obtained using ammonium sulfate as a precipitant with sodium citrate-boric acid-citric acid buffered pH 4.5. The acid pH crystal form resulted from a study aimed at developing conditions favorable to sitting drop vapour diffusion crystallization of other abalone lysins which do not crystallize at neutral or basic pH conditions. The space group is P2221 with cell parameters a = 51.2, b = 47.0, c = 128.8 Å with two molecules per asymmetric unit.
In the above paper we demonstrate that ammonium sulfate and ammonium thiocyanate act as co-precipitants. This conclusion is important for the application of reverse screening
where the effect of thiocyanate on basic proteins is considered a "specific" effect. In
reverse screening a precipitant should not have specific effects. Hence, by using the combination of
ammonium sulfate and thiocyanate we can gain better control over the crystallization parameters.
In reverse screening compounds that give specific effects are considered additives. Take a look at the different crystal morphologies that result from the use
of additives in Figure 1 in the paper.