Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0149514 (bronchitis)
 6,902 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The first membrane-spanning domain (m1) of the model cis Golgi protein M (formerly called E1) from the avian coronavirus infectious bronchitis virus is required for targeting to the Golgi complex. When inserted in place of the membrane-spanning domain of a plasma membrane protein (vesicular stomatitis virus G protein), the chimeric protein ("Gm1") is retained in the Golgi complex of transfected cells. To determine the precise features of the m1 domain responsible for Golgi targeting, we produced single amino acid substitutions in m1 and analyzed their effects on localization of Gm1. Expression at the plasma membrane was used as the criterion for loss of Golgi retention. Rates of oligosaccharide processing were used as a measure of rate and efficiency of transport through the Golgi complex. We identified four uncharged polar residues that are critical for Golgi retention of Gm1 (Asn465, Thr469, Thr476, and Gln480). These residues line one face of a predicted alpha-helix. Interestingly, when the m1 domain of the homologous M protein from mouse hepatitis virus is inserted into the G protein reporter, the chimeric protein is not efficiently retained in the Golgi complex, but transported to the cell surface. Although it possesses three of the four residues we identified as important in the avian m1 sequence, other residues in the membrane-spanning domain from the mouse protein must prevent efficient recognition of the polar face within the lipid bilayer of the cis Golgi.
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PMID:Retention of a cis Golgi protein requires polar residues on one face of a predicted alpha-helix in the transmembrane domain. 840 Apr 55

Golgi resident proteins maintain their localization despite a continual protein and lipid flux through the organelle. To study Golgi retention mechanisms, we have focused upon the chimeric protein Gm1. This protein contains the Golgi transmembrane domain targeting signal from the infectious bronchitis virus M protein and the lumenal and cytoplasmic domain of the vesicular stomatitis virus glycoprotein (VSV G). The Gm1 protein is targeted to the Golgi where it forms an unusually stable detergent-resistant oligomer. The formation of oligomeric structures may aid retention of Golgi resident proteins. Thus, determining the stabilization mechanism may shed light on Golgi protein retention. Previous work determined that the transmembrane domain is required for the targeting and oligomerization of Gm1, but it is the cytoplasmic tail that stabilizes the complexes [Weisz, O. A., Swift, A. M., and Machamer, C. E. (1993) J. Cell Biol. 122, 1185-1196]. However, further study of the oligomer has been difficult due to its insolubility. Here we report that fragmenting the Gm1 protein into several pieces facilitates solubilization by sodium dodecyl sulfate (SDS). By analyzing the fragments produced after cleavage, we determined that the stability of the oligomer is not caused by covalent linkage of Gm1 to itself or other proteins. The fragment corresponding to the transmembrane domain and tail of Gm1 had an enhanced mobility in SDS gels relative to the same fragment of the parent VSV G protein. The enhanced migration of the tail fragment does not reflect sequence differences or post-translational modification, but correlates with Golgi localization and oligomerization. We suggest that the enhanced mobility of the Gm1 tail fragment reflects an altered conformation which serves to stabilize the detergent-resistant oligomers.
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PMID:Fragmentation of a Golgi-localized chimeric protein allows detergent solubilization and reveals an alternate conformation of the cytoplasmic domain. 942 38