4b3g
From Proteopedia
crystal structure of Ighmbp2 helicase in complex with RNA
Structural highlights
DiseaseSMBP2_HUMAN Defects in IGHMBP2 are the cause of distal hereditary motor neuronopathy type 6 (HMN6) [MIM:604320; also known as spinal muscular atrophy distal autosomal recessive 1 (DSMA1) or spinal muscular atrophy with respiratory distress 1 (SMARD1). Distal hereditary motor neuronopathies constitute a heterogeneous group of neuromuscular disorders caused by selective degeneration of motor neurons in the anterior horn of the spinal cord, without sensory deficit in the posterior horn. The overall clinical picture consists of a classical distal muscular atrophy syndrome in the legs without clinical sensory loss. The disease starts with weakness and wasting of distal muscles of the anterior tibial and peroneal compartments of the legs. Later on, weakness and atrophy may expand to the proximal muscles of the lower limbs and/or to the distal upper limbs. The most prominent symptoms of HMN6 are severe respiratory distress resulting from diaphragmatic paralysis with eventration shown on chest x-ray and predominant involvement of the upper limbs and distal muscles.[1] [2] [3] [4] [5] [6] [7] FunctionSMBP2_HUMAN 5' to 3' helicase that unwinds RNA and DNA duplices in an ATP-dependent reaction. Acts as a transcription regulator. Required for the transcriptional activation of the flounder liver-type antifreeze protein gene. Exhibits strong binding specificity to the enhancer element B of the flounder antifreeze protein gene intron. Binds to the insulin II gene RIPE3B enhancer region. May be involved in translation (By similarity). DNA-binding protein specific to 5'-phosphorylated single-stranded guanine-rich sequence related to the immunoglobulin mu chain switch region. Preferentially binds to the 5'-GGGCT-3' motif. Interacts with tRNA-Tyr. Stimulates the transcription of the human neurotropic virus JCV.[8] [9] Publication Abstract from PubMedMutations in immunoglobulin micro-binding protein 2 (Ighmbp2) cause distal spinal muscular atrophy type 1 (DSMA1), an autosomal recessive disease that is clinically characterized by distal limb weakness and respiratory distress. However, despite extensive studies, the mechanism of disease-causing mutations remains elusive. Here we report the crystal structures of the Ighmbp2 helicase core with and without bound RNA. The structures show that the overall fold of Ighmbp2 is very similar to that of Upf1, a key helicase involved in nonsense-mediated mRNA decay. Similar to Upf1, domains 1B and 1C of Ighmbp2 undergo large conformational changes in response to RNA binding, rotating 30 degrees and 10 degrees , respectively. The RNA binding and ATPase activities of Ighmbp2 are further enhanced by the R3H domain, located just downstream of the helicase core. Mapping of the pathogenic mutations of DSMA1 onto the helicase core structure provides a molecular basis for understanding the disease-causing consequences of Ighmbp2 mutations. The Ighmbp2 helicase structure reveals the molecular basis for disease-causing mutations in DMSA1.,Lim SC, Bowler MW, Lai TF, Song H Nucleic Acids Res. 2012 Sep 10. PMID:22965130[10] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. Loading citation details.. Citations No citations found References
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