The STAT1 K201N mutation caused susceptibility to mycobacterial and viral infections. (A) The human STAT1 coding region with its known mutations. Coding exons are numbered with Roman numerals and delineated by vertical bars. The N-terminal domain, coiled-coil domain, DNA-binding domain, linker domain, SH2 domain, tail segment domain (TS), and transactivation domain (TD) are indicated, together with their amino acid boundaries. Phosphorylation sites, Tyr 701 (pY) and Ser 727 (pS), are indicated. Mutations in red are recessive mutations associated with complete STAT1 deficiency. Mutations in green are heterozygous mutations associated with partial dominant STAT1 deficiency. Mutations in blue are recessive mutations associated with partial recessive STAT1 deficiency. The mutation reported here is indicated in italics. (B) The pedigree, phenotype, and genotype of the consanguineous kindred from Saudi Arabia. The proband, P1, II.1 is indicated by an arrow, and presented with disseminated M avium infection and disseminated varicella. II.3 had disseminated BCG infection and died of septic shock at the age of 3. These 2 patients are referred to as P1 and P2, respectively. I.1 and I.2 are first cousins. (C) Genomic sequence analysis of exon 8 showing a homozygous G → T mutation in P1, leading to the replacement of a lysine residue by an asparagine residue (K201N/K201N) at position 201 of the protein.