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Crystal structure of BRAF:MEK1 complexCrystal structure of BRAF:MEK1 complex
Structural highlights
DiseaseBRAF_HUMAN Note=Defects in BRAF are found in a wide range of cancers.[1] Defects in BRAF may be a cause of colorectal cancer (CRC) [MIM:114500.[2] Defects in BRAF are involved in lung cancer (LNCR) [MIM:211980. LNCR is a common malignancy affecting tissues of the lung. The most common form of lung cancer is non-small cell lung cancer (NSCLC) that can be divided into 3 major histologic subtypes: squamous cell carcinoma, adenocarcinoma, and large cell lung cancer. NSCLC is often diagnosed at an advanced stage and has a poor prognosis.[3] [4] Defects in BRAF are involved in non-Hodgkin lymphoma (NHL) [MIM:605027. NHL is a cancer that starts in cells of the lymph system, which is part of the body's immune system. NHLs can occur at any age and are often marked by enlarged lymph nodes, fever and weight loss.[5] [6] Defects in BRAF are a cause of cardiofaciocutaneous syndrome (CFC syndrome) [MIM:115150; also known as cardio-facio-cutaneous syndrome. CFC syndrome is characterized by a distinctive facial appearance, heart defects and mental retardation. Heart defects include pulmonic stenosis, atrial septal defects and hypertrophic cardiomyopathy. Some affected individuals present with ectodermal abnormalities such as sparse, friable hair, hyperkeratotic skin lesions and a generalized ichthyosis-like condition. Typical facial features are similar to Noonan syndrome. They include high forehead with bitemporal constriction, hypoplastic supraorbital ridges, downslanting palpebral fissures, a depressed nasal bridge, and posteriorly angulated ears with prominent helices. The inheritance of CFC syndrome is autosomal dominant.[7] Defects in BRAF are the cause of Noonan syndrome type 7 (NS7) [MIM:613706. Noonan syndrome is a disorder characterized by facial dysmorphic features such as hypertelorism, a downward eyeslant and low-set posteriorly rotated ears. Other features can include short stature, a short neck with webbing or redundancy of skin, cardiac anomalies, deafness, motor delay and variable intellectual deficits.[8] [9] Defects in BRAF are the cause of LEOPARD syndrome type 3 (LEOPARD3) [MIM:613707. LEOPARD3 is a disorder characterized by lentigines, electrocardiographic conduction abnormalities, ocular hypertelorism, pulmonic stenosis, abnormalities of genitalia, retardation of growth, and sensorineural deafness.[10] [11] Note=A chromosomal aberration involving BRAF is found in pilocytic astrocytomas. A tandem duplication of 2 Mb at 7q34 leads to the expression of a KIAA1549-BRAF fusion protein with a constitutive kinase activity and inducing cell transformation.[12] FunctionBRAF_HUMAN Involved in the transduction of mitogenic signals from the cell membrane to the nucleus. May play a role in the postsynaptic responses of hippocampal neuron. Publication Abstract from PubMedRAF family kinases are RAS-activated switches that initiate signaling through the MAP kinase cascade to control cellular proliferation, differentiation and survival(1-3). RAF activity is tightly regulated, and inappropriate activation is a frequent cause of cancer(4-6). At present, the structural basis of RAF regulation is poorly understood. Here we describe autoinhibited and active state structures of full-length BRAF in complexes with MEK1 and a 14-3-3 dimer, determined using cryo-electron microscopy (cryo-EM). A 4.1 A resolution cryo-EM reconstruction reveals an inactive BRAF-MEK1 complex restrained in a cradle formed by the 14-3-3 dimer, which binds the phosphorylated S365 and S729 sites that flank the BRAF kinase domain. The BRAF cysteine-rich domain (CRD) occupies a central position that stabilizes this assembly, but the adjacent RAS-binding domain (RBD) is poorly ordered and peripheral. The 14-3-3 cradle maintains autoinhibition by sequestering the membrane-binding CRD and blocking dimerization of the BRAF kinase domain. In the active state, these inhibitory interactions are released and a single 14-3-3 dimer rearranges to bridge the C-terminal pS729 binding sites of two BRAFs, driving formation of an active, back-to-back BRAF dimer. Our structural snapshots provide a foundation for understanding normal RAF regulation and its mutational disruption in cancer and developmental syndromes. Architecture of autoinhibited and active BRAF-MEK1-14-3-3 complexes.,Park E, Rawson S, Li K, Kim BW, Ficarro SB, Pino GG, Sharif H, Marto JA, Jeon H, Eck MJ Nature. 2019 Oct 3. pii: 10.1038/s41586-019-1660-y. doi:, 10.1038/s41586-019-1660-y. PMID:31581174[13] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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