The structure of Na2[Zr(SO4)3].3H20 has been determined'~y single-crystal X-ray analysis and refined by least-squares. The crystals, which are orthorhombic with space group P21212t, have the unit-ceU dimensions a=22.16, b=7.73, c=7.08 /~. The structure consists of spirals of composition [Zr(SO4)a(H20)2], extending in the [001] direction which are held together by the sodium atoms and a single lattice water molecule. Two of the sulphate groups form bridges between the zirconium atoms while two more sulphate groups are each doubly bonded to each zirconium atom. All sulphate groups have two terminal oxygen atoms. There are two water molecules coordinated to each zirconium atom. The hydrogen atoms of these water molecules bridge to oxygen atoms of sulphate groups and probably give rigidity to the spiral structure.

Various closely related programs for the calculation of the rotation function are described. The latter explores systematically the amount of overlap between two differently oriented Patterson syntheses, and can be used to relate similar molecules or structures in the same or different crystals. The calculations require only the intensities rather than the Patterson sections. It is shown that (i) neglecting all but 10 ~ of the largest intensities for one of the structures and (ii) construction of a table of the transform G, of the spherical volume within which the Patterson functions are being compared, sampled in a 5 x 5 x 5 grid within the reciprocal unit cell, gives considerable improvement in computing time without excess loss of accuracy. The effect of premature truncation or coarseness of the G table is discussed, together with other considerations which are important in the successful application of this technique.

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SMYD2 is a protein lysine methyltransferase with a broad substrate specificity and able to methylate both histone and non‐histone proteins such as histone H3 and H4, p53, retinoblastoma‐associated protein 1, and PTEN. However, how SMYD2 substrate specificity is precisely controlled and balanced over such a large number of targets remains elusive. Poly(ADP‐ribose) polymerase‐1 (PARP1) is another known SMYD2 substrate, acting as a first responder to DNA damage. SMYD2 mono‐methylates PARP1 at lysine 528 within the auto‐modification region. Methylated PARP1 positively regulates the poly(ADP‐ribosyl)ation activity and enhances cellular poly(ADP‐ribose) formation after oxidative stress. In this study, we determined the crystal structure of SMYD2 in complex with a K528‐containing PARP1 peptide. Unexpectedly, two peptide binding sites were identified from the structure, one corresponding to the known substrate binding site and the other a new secondary binding site. We found that the point mutations of the secondary binding site completely abolished binding of the PARP1 peptide to both sites in the isothermal titration calorimetry (ITC) analysis. The crystal structures of the corresponding SMYD2 mutants also showed disturbed binding, in which the mutation did not cause any significant structural changes but no peptide binding was observed. However, in the context of PARP1 protein, the same mutation enhanced the interaction in the ELISA assay, which was partially correlated with its substrate‐specific effects on the enzyme activities. The mutation of the secondary binding site mutation enhanced SMYD2 activity on histone H3 protein but attenuated the methylation of PARP1 protein, and there was no significant effect on histone H4 protein. Overall, our study revealed a new peptide binding site in SMYD2 that may play a regulatory role in the SMYD2 substrate selectivity.