Structure-Activity Relationship of the Leucine-based Sorting Motifs in the Cytosolic Tail of the Major Histocompatibility Complex-associated Invariant Chain (*)
- Andrea Motta(1)(§),
- Bjørn Bremnes(2),
- Maria A. Castiglione Morelli(3),
- Rainer W. Frank(4),
- Gabriella Saviano(1) and
- Oddmund Bakke(§)(2)
- From the (1) From Istituto per la Chimica di Molecole di Interesse Biologico del CNR, I-80072 Arco Felice (Napoli), Italy, the
- (2) Division of Molecular Cell Biology, Department of Biology, University of Oslo, N-0316 Oslo, Norway, the
- (3) Dipartimento di Chimica, Università della Basilicata, I-85100 Potenza, Italy, and the
- (4) Zentrum für Molekulare Biologie, Universität Heidelberg, Postfach 106249, D-69052 Heidelberg, Federal Republic of Germany
- § To whom correspondence should be addressed (to one of these authors): Dr. A. Motta, Istituto per la Chimica di Molecole di Interesse Biologico del CNR, I-80072 Arco Felice (Napoli), Italy (Tel.: 39-81-8534-218/262; Fax: 39-81-8041-770; amot{at}nmr.icmib.na.cnr.it) or Dr. O. Bakke, Division of Molecular Cell Biology, Dept. of Biology, University of Oslo, N-0316 Oslo, Norway (Fax: 47-22-854-605; obakke{at}bio.uio.no.
Abstract
The cytosolic tail of the major histocompatibility complex-associated invariant chain protein contains two Leu-based motifs
that both mediate efficient sorting to the endocytic pathway. Nuclear magnetic resonance data on a peptide of 27 residues
corresponding to the cytosolic tail of human invariant chain indicate that in water at pH 7.4 the membrane distal motif Leu
-Ile
lies within a nascent helix, while the membrane proximal motif Met
-Leu
is part of a turn. The presence of a small amount of methanol stabilizes an α helix from Gln
to Leu
with a kink on Pro
. Point mutations of the cytosolic tail of the protein suggest that amino-terminal residues located in spatial proximity to
the Leu motifs contribute to efficient internalization and targeting to endosomes in transfected COS cells. Residues on the
spatially opposite side of the Leu motifs were, on the other hand, mutated with no measurable effect on targeting. Structural
and biological data thus suggest that the signals are not continuous but consist of “signal patches” formed by the three-dimensional
structure of the cytosolic tail of invariant chain.
Footnotes
-
↵* This work was supported by grants from the Italian National Research Council (to A. M.), the Norwegian Research Council (to O. B. and B. B.), and the Norwegian Cancer Society (to O. B.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵1 The abbreviations used are:
- TGN
-
trans-Golgi network
- Ii
-
invariant chain
- INA
-
chimeric protein obtained by fusing neuraminidase (NA) to the cytosolic tail of Ii
- DQF-COSY
-
double-quantum-filtered correlated spectroscopy
- NOE
-
nuclear Overhauser enhancement
- NOESY
-
two-dimensional NOE spectroscopy
- TOCSY
-
total correlation spectroscopy
- DMEM-FCS
-
Dulbecco's modified Eagle's medium supplemented with 10% fetal calf serum.
-
↵2 S. Ness, personal communication.
-
↵3 A. Motta, B. Bremnes, M. A. Castiglione Morelli, R. W. Frank, G. Saviano, and O. Bakke, unpublished data.
-
↵4 M. Gedde-Dahl, I. Freiswinkel, M. Stascheschewski, K. Schenck, N. Koch, and O. Bakke, submitted for publication.
-
↵5 A. Motta, M. A. Castiglione Morelli, B. Bremnes, and O. Bakke, manuscript in preparation.
-
- Received June 12, 1995.
- Revision received August 2, 1995.
- © 1995 by The American Society for Biochemistry and Molecular Biology, Inc.
