Mammalian members of the Sp1-like/KLF family. (a) A phylogenetic tree of human Sp1-like/KLF proteins and mouse Sp5 and Sp6 (mSp5 and mSp6) identifies three general subgroups. Subgroup I consists of the proteins most highly related to Sp1 (Sp1-Sp6). The other Sp1-like/KLF proteins are divided into two additional groups (subgroups II and III). The tree was generated using Genetic Computer Group (GCG) sequence analysis software. (b) Sequence alignment of the zinc-finger domains of Sp1-like/KLF protein family members. The sequence of the zinc-finger motifs of human Sp1 was compared with the corresponding regions of previously identified human Sp1-like proteins and with mouse Sp5. The consensus zinc fingers (ZF1, ZF2 and ZF3) are indicated below the sequences and the amino-acid residues predicted to interact with DNA according to the Klevit model  are indicated by arrows. Identical residues are in black, similar residues in gray and different residues in lower case. The percentage similarity between the Sp1 and the other Sp1-like/KLF zinc-finger domains is indicated on the right. Note that the amino acids predicted to make contact with DNA within the first (KHA), second (RER) and third (RHK) zinc-finger domains of Sp1 are nearly identical to the corresponding regions of other members of the Sp1-like/KLF family. All sequences are available in the NCBI human genome database .