Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.3.1 (alkaline phosphatase)
 47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

MP20 is an intrinsic membrane protein previously identified in mammalian lens fiber cells. To identify a possible role for this protein in the lens, the distribution of MP20 and connexin46 has now been examined. Western immunoblotting with an anti-peptide antibody generated to the C-terminal 8 amino acids of MP20 confirmed the presence of this protein in the lens of several different mammalian species. A monoclonal antibody 5H1 was prepared that, in Western blots of bovine lesn membranes, recognized the same component as an antibody to rat connexin46 (Cx46). The apparent molecular mass of this component decreased from 59 kDa to 55 kDa following treatment of lens membranes with alkaline phosphatase. A monoclonal antibody to connexin-related MP70 recognized a 70 kDa component in bovine lens membranes confirming the presence of these two different connexin proteins in bovine lens membranes. To localize MP20 and Cx46 in the bovine lens membrane, lens fiber cell bundles were immunofluorescently labeled with both the MP20 antibody, and the monoclonal antibody to Cx46. Cx46 was identified in large plaques on the broad faces of the lens fiber cells throughout the outer 1 mm of the lens cortex. MP20 colocalized with Cx46 only in a restricted area 0.5 mm to 1.0 mm into the lens. In other regions of the lens, MP20 appeared more diffusely distributed over the fiber cell surface, although apparently concentrated in the ball-and-socket regions at the corners of the narrow side of the inner cortical lens fiber cells. These inner cortical regions were devoid of Cx46. A difference in distribution of these two proteins was confirmed in studies of immunofluorescently labeled lens cryosections. Furthermore, immunogold electron microscopy of purified lens membranes identified MP20 in both junctional regions (with Cx46) and in single membranes. These results provide evidence for a role for MP20 in mammalian lens fiber cell junctional formation or organization.
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PMID:The distribution of the fiber cell intrinsic membrane proteins MP20 and connexin46 in the bovine lens. 133 Nov 34

Cell-to-cell channels composed of connexin44 and connexin50 were purified from plasma membranes of calf and fetal bovine lenses. The channels were treated with the nonionic detergents octyl-beta-D-glucopyranoside and decyl-beta-D-maltopyranoside, and the channel/detergent complexes purified by ion and gel filtration column chromatography. In negative staining, the channels appeared as annuli 11 +/- 0.6 nm (s.d., n = 105) in diameter and as 16 +/- 0.8 nm (s.d., n = 96) long particles which corresponded to top and side views of 'complete' cell-to-cell channels. The purified cell-to-cell channels were composed principally of a protein, called MP70, that appeared as a diffuse 55-75 kDa band in SDS-PAGE. Dephosphorylation with alkaline phosphatase transformed the diffuse 55-75 kDa band into two distinct bands of almost equal intensity. Immunoblotting showed the bands to be connexin44 and connexin50, respectively. The antibodies also recognized weaker bands composed of the unphosphorylated form of both connexins. The connexins appear to be processed independently 'in vivo'. The unphosphorylated form of connexin50 was present in channels and membranes from fetal, calf and adult bovine lenses, while unphosphorylated connexin44 only in channels purified from fetal lenses. Therefore, lens cell-to-cell channels are composed principally of equal amounts of phosphorylated connexins 44 and 50 that appear to be assembled in the same channel ('hybrid').
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PMID:Purification of bovine lens cell-to-cell channels composed of connexin44 and connexin50. 853 48