Catalyzes the specific attachment of an amino acid to its cognate tRNA in a 2 step reaction: the amino acid (AA) is first activated by ATP to form AA-AMP and then transferred to the acceptor end of the tRNA. When secreted, acts as a signaling molecule that induces immune response through the activation of monocyte/macrophages. Catalyzes the synthesis of diadenosine oligophosphate (Ap4A), a signaling molecule involved in the activation of MITF transcriptional activity. Interacts with HIV-1 virus GAG protein, facilitating the selective packaging of tRNA(3)(Lys), the primer for reverse transcription initiation.
Defects in KARS are the cause of Charcot-Marie-Tooth disease recessive intermediate type B (CMTRIB) [MIM:613641]; also called Charcot-Marie-Tooth neuropathy recessive intermediate B. CMTRIB is a form of Charcot-Marie-Tooth disease, a disorder of the peripheral nervous system, characterized by progressive weakness and atrophy, initially of the peroneal muscles and later of the distal muscles of the arms. Recessive intermediate forms of Charcot-Marie-Tooth disease are characterized by clinical and pathologic features intermediate between demyelinating and axonal peripheral neuropathies, and motor median nerve conduction velocities ranging from 25 to 45 m/sec.
Belongs to the class-II aminoacyl-tRNA synthetase family.
The N-terminal domain (1-65) of the cytoplasmic isoform is a functional tRNA-binding domain (By similarity), is required for nuclear localization, is involved in the interaction with DARS, but has a repulsive role in the binding to EEF1A1. A central domain (208-259) is involved in homodimerization and is required for interaction with HIV-1 GAG and incorporation into virions. The C-terminal domain (452-597) is not required for interaction with AIMP2.
Mitochondrion and Cytoplasm. Nucleus. Cell membrane. Secreted. Secretion is induced by TNF-alpha.