Ribbon diagram of human Insulin receptor substrate 1 pleckstrin homology domain showing that serine 24 (spheres) lies in close proximity to the basic residues (red sticks) implicated in lipid binding (i.e. Lys 21, Lys 23, His 26, Arg 28, Lys 61 and Arg 62). Nawaratne et al. show that Serine 24 is phosphorylated by PKCs and this inhibits protein-lipid interactions of IRS-1.

Regulation of Insulin Receptor Substrate 1 Pleckstrin Homology Domain By Protein Kinase C: Role of Serine 24 Phosphorylation.
Nawaratne R, Gray A, Jorgensen CH, Downes CP, Siddle K, Sethi JK
Mol Endocrinol. 2006 Epub ahead of print