The major intrinsic protein (MIP) of the bovine lens fiber membrane: Characterization and structure based on cDNA cloning

Gorin, Michael B.; Yancey, S B; Cline, Janice; Revel, Jean‐Paul; Horwitz, Joseph

doi:10.1016/0092-8674(84)90190-9

Cited by 508 publications

(229 citation statements)

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“…Although questions remain about the biological role of MP26 [3], evidence indicates it is found within lens intercellular junctions [4] and is capable of forming membrane channels [5-81. The sequence of MP26 has recently been determined from cDNA clones and the authors offer a model for the structure of MP26 within a lipid membrane [9]. This model, based on hydrophobicity analysis and other techniques, is consistent with MP26 monomers associating to form a hydrophilic channel.…”

mentioning

confidence: 77%

“…The marked calcium and phospholipid specificity of the phosphorylation activity indicated that contaminating protein kinases did not contribute significantly to the observed protein-kinase-c-dependent phosphorylation. With both the trichloroacetic acid [9]. Possible phosphorylation and protease cleavage sites are emphasized assay and SDS-PAGE (Fig.l), removing calcium, with or without CAMP addition, dramatically reduced the labeling of histone H1 or lens membranes to background levels.…”

Section: Properties Of Protein Kinase C Preparationsmentioning

confidence: 99%

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Phosphorylation of lens intrinsic membrane proteins by protein kinase C

Lampe¹,

Bazzi

Nelsestuen

et al. 1986

Eur J Biochem

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Two intrinsic proteins of bovine lens membranes with apparent relative molecular masses (MI, aPP) of 26000 and 18000 were phosphorylated in intact membranes by protein kinase C prepared from either bovine brain or lens. The kinase preparations exhibited histone H 1 phosphorylation dependent on calcium and phospholipid but not on CAMP. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis of the lens membranes showed a major band at MI, app = 26000 (identified as MP26, the main intrinsic protein of lens fiber cells), an intermediate band at Mr, app = 18000 and several minor bands. Autoradiography of complete assay mixture containing protein kinase C, calcium, magnesium and [Y-~'P]ATP showed major bands at MI, app = 18000 and 26000. Several lines of evidence indicated that the label at MI, app = 26000 was associated with MP26, a protein which has been found in lens junctions and which may form cell-cell channels. Treatment of the phosphorylated membranes with chymotrypsin and V 8 protease cleaved the major band at M,, app = 26000 to fragments of M,, app = 22000 and 24000. Label was not,detected in the resulting MI, app = 22000 peptide, but the MI, app = 24000 peptide was found to be labeled. Phosphoamino acid analysis of MP26 indicated that approximately 75% of the label was on phosphoserine and 25% was on phosphothreonine. No label was found on phosphotyrosine. These results differ from those reported for CAMP-dependent phosphorylation of lens proteins. Phosphorylation by protein kinase C may account for some of the labeling of MP26 detected in vivo.Lens membranes contain a major intrinsic protein, often referred to as MP26 or MIP26 due to the apparent MI on SDS-PAGE of 26000 [l]. MP26 constitutes approximately a half of the total intrinsic protein of the lens membrane [2]. Although questions remain about the biological role of MP26 [3], evidence indicates it is found within lens intercellular junctions [4] and is capable of forming membrane channels [5-81. The sequence of MP26 has recently been determined from cDNA clones and the authors offer a model for the structure of MP26 within a lipid membrane [9]. This model, based on hydrophobicity analysis and other techniques, is consistent with MP26 monomers associating to form a hydrophilic channel. The relative molecular mass of MP26 is 28200 based on this sequence. Thus, MP26 has several features in common with gap junction proteins considered in a variety of tissues [lo-121.The regulation of gap-junction-dependent communication is not well understood in any tissue. However, it is known that the permeability of junctions between different cells can be reduced by elevated cytoplasmic concentrations of calcium and hydrogen ions [13, 141. In addition, agents or manipulations that elevate the cytoplasmic levels of CAMP have been reported to decrease rapidly and reversibly the Correspondence to

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mentioning

confidence: 77%

Section: Properties Of Protein Kinase C Preparationsmentioning

confidence: 99%

Phosphorylation of lens intrinsic membrane proteins by protein kinase C

Lampe¹,

Bazzi

Nelsestuen

et al. 1986

Eur J Biochem

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“…The lens fiber protein (MIP 26), for which the entire sequence has been determined [20], has no homology with the connexin proteins. In addition, a 16 kDa protein isolated from different species and phyla has frequently been propounded as the major structural component of gap junctions [6,7].…”

Section: Resultsmentioning

confidence: 99%

A 16 kDa protein co‐isolating with gap junctions from brain tissue belonging to the class of proteolipids of the vacuolar H⁺‐ATPases

et al. 1989

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A 16 kDa protein from an enriched gap junction preparation was isolated from bovine brain tissues. N-terminal amino acid microsequencing of the first 20 amino acids showed a complete homology with a recently published sequence of a proteolipid from a vacuolar H ÷-ATPase from chromaffin granules. Incubation of the brain gap junction preparation with 14C-N,N'-dicyclohexylcarbodiimide showed a significant binding of this compound to the 16 kDa protein, indicating that a proton binding site also occurs within that particular protein. The data suggest that this 16 kDa protein, which has also been described in gap junction preparations from various other tissues, belongs to the proton transporting ATPase.

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“…The molecular model of MP26 based on amino acid analysis and cDNA cloning [1] conceives the existence of six transmembrane a-helical domains and the presence of the NH2 and COOH terminal segments exposed at the cytoplasmic side of the membrane. It is remarkable that among these a-helices, one of them displays an amphipathic nature which might generate a potential domain for the hydrophilic transmembrane channel.…”

Section: Introductionmentioning

confidence: 99%

High‐performance liquid chromatography of the main polypeptide (MP26) of lens fiber plasma membranes solubilized with n‐octyl β‐D‐glucopyranoside

et al. 1988

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The main polypeptide isolated from lens fiber membrane has been solubilized in octyl glucoside and studied by gel filtration in high-performance liquid chromatography (HPLC). The combination of S20,w value obtained from analytical ultracentrifugation and Stokes radius determined by HPLC of the soluble fraction indicates that more than 90% of the protein is monomeric. The solubilization of the protein seems to be dependent upon the presence of the NH 2 and COOH terminal sequences, since proteolytic degradation of MP26 which removes these terminal sequences is less soluble than the uncleaved polypeptide. Moreover, there is a higher amount of oligomer after proteolysis. Fatty acid analysis by gas chromatography shows that the insoluble membrane fraction from both cortical and nuclear fibers comprises a special class of long (C22) saturated fatty acids (behenic acid).

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The major intrinsic protein (MIP) of the bovine lens fiber membrane: Characterization and structure based on cDNA cloning

Cited by 508 publications

References 57 publications

Phosphorylation of lens intrinsic membrane proteins by protein kinase C

Phosphorylation of lens intrinsic membrane proteins by protein kinase C

A 16 kDa protein co‐isolating with gap junctions from brain tissue belonging to the class of proteolipids of the vacuolar H⁺‐ATPases

High‐performance liquid chromatography of the main polypeptide (MP26) of lens fiber plasma membranes solubilized with n‐octyl β‐D‐glucopyranoside

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The major intrinsic protein (MIP) of the bovine lens fiber membrane: Characterization and structure based on cDNA cloning

Cited by 508 publications

References 57 publications

Phosphorylation of lens intrinsic membrane proteins by protein kinase C

Phosphorylation of lens intrinsic membrane proteins by protein kinase C

A 16 kDa protein co‐isolating with gap junctions from brain tissue belonging to the class of proteolipids of the vacuolar H+‐ATPases

High‐performance liquid chromatography of the main polypeptide (MP26) of lens fiber plasma membranes solubilized with n‐octyl β‐D‐glucopyranoside

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A 16 kDa protein co‐isolating with gap junctions from brain tissue belonging to the class of proteolipids of the vacuolar H⁺‐ATPases