Structural domains in phospholemman: A possible role for the carboxyl terminus in channel inactivation

Zhenhui Chen, Larry Jones, Jeffrey J. O'Brian, J. Randall Moorman, Steven E. Cala

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

Phospholemman (PLM) is a small (72-amino acid) transmembrane protein found in cardiac sarcolemma that is a major substrate for several protein kinases in vivo. Detailed structural data for PLM is lacking, but several studies have described an ion conductance that results from PLM expression in oocytes. Moreover, addition of purified PLM to lipid bilayers generates similar ion currents, suggesting that the PLM molecule itself might be sufficient for channel formation. To provide a framework for understanding the function of PLM, we investigated PLM topology and structure in sarcolemmal membrane vesicles and analyzed purified recombinant PLM. Immunoblot analyses with site-specific antibodies revealed that the extracellular segment (residues 1 to 17) exists in a protected configuration highly resistant to proteases, even in detergent solutions. The intracellular portion of the molecule (residues 38 to 72), in contrast, was highly susceptible to proteases. Trypsin treatment produced a limit peptide (residues 1 to 43), which showed little change in electrophoretic mobility in SDS gels and retained the ion-channel activity in lipid bilayers that is characteristic of the full-length protein. In addition, we found that conductance through PLM channels exhibited rapid inactivation during depolarizing ramps at voltages greater than ±50 mV, Channels formed by trypsinized PLM or recombinant PLM 1-43 exhibited dramatic reductions in voltage-dependent inactivations. Our data point to distinct domains within the PLM molecule that may correlate with functional properties of channel activity observed in oocytes and lipid bilayers.

Original languageEnglish
Pages (from-to)367-374
Number of pages8
JournalCirculation Research
Volume82
Issue number3
StatePublished - Feb 23 1998

Fingerprint

Lipid Bilayers
Oocytes
phospholemman
Peptide Hydrolases
Ions
Sarcolemma
Architectural Accessibility
Ion Channels
Detergents
Trypsin
Protein Kinases
Proteins
Gels
Amino Acids
Peptides
Membranes
Antibodies

Keywords

  • Ion channel topology
  • Phospholemman
  • Sarcolemma

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

Cite this

Structural domains in phospholemman : A possible role for the carboxyl terminus in channel inactivation. / Chen, Zhenhui; Jones, Larry; O'Brian, Jeffrey J.; Randall Moorman, J.; Cala, Steven E.

In: Circulation Research, Vol. 82, No. 3, 23.02.1998, p. 367-374.

Research output: Contribution to journalArticle

Chen, Zhenhui ; Jones, Larry ; O'Brian, Jeffrey J. ; Randall Moorman, J. ; Cala, Steven E. / Structural domains in phospholemman : A possible role for the carboxyl terminus in channel inactivation. In: Circulation Research. 1998 ; Vol. 82, No. 3. pp. 367-374.
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