Biochemistry. In the article “The putative actin-binding role of hydrophobic residues Trp⁵⁴⁶ and Phe⁵⁴⁷ in chicken gizzard heavy meromyosin” by Hirofumi Onishi, Manuel F. Morales, Kazuo Katoh, and Keigi Fujiwara, which appeared in number 26, December 19, 1995 of Proc. Natl. Acad. Sci. USA (92, 11965–11969), the authors request that the following be noted. In the Results section under “Enzymatic Properties,” 104 and 19 μM⁻¹ should be 1.04 × 10⁴ and 1.9 × 10³ M⁻¹, respectively. In the last column of Table 1, 22, 104, 27, and 19 μM⁻¹ should be 2.2 × 10³, 1.04 × 10⁴, 2.7 × 10³, and 1.9 × 10³ M⁻¹, respectively. The correct table is shown below.

Table 1.

ATPase activities of wild-type and mutant HMMs

HMM	MgATPase, nmol of Pi per min per mg of protein		Actin-activated MgATPase
	High salt	Low salt	Vmax, nmol of Pi per min per mg	Ka, M−1 × 10−3
Wild-type
−kinase	3.7	1.3	76	2.2
+kinase	—	3.2	637	10.4
Mutant
−kinase	4.4	2.7	49	2.7
+kinase	—	5.8	65	1.9

V_max is the maximum actin-activated ATPase activity of HMM and K_a is the apparent binding constant for HMM to actin, which is defined to be the reciprocal of the apparent K_m from the double reciprocal plots (Fig. 4). To phosphorylate the regulatory light chain of HMM, myosin light chain kinase, calmodulin, and Ca²⁺ were added to the ATPase assay medium. —, Not measured.