This volume is the first book-length survey of caveolae and lipid rafts. Interest has
developed rapidly in the role of these surface microdomains in such diverse fields
as transmembrane signaling, cell locomotion, vascular relaxation, senescence, and
the uptake and exit from cells of viruses and bacteria. Individual chapters in this
volume cover areas as diverse as the forces that induce and maintain membrane
invaginations, and the clinical relevance of multiprotein complexes at the cell surface,
defects in which are associated with cancer, and Alzheimer’s and prion-dependent
Technical advancements are basic elements in our life. In biophysical studies, new applications and improvements in well-established techniques are being implemented every day. This book deals with advancements produced not only from a technical point of view, but also from new approaches that are being taken in the study of biophysical samples, such as nanotechniques or single-cell measurements.
K-Ras is a small G-protein, localized mainly at the inner leaflet of the
plasma membrane. The membrane targeting signal of this protein consists
of a polybasic C-terminal sequence of six contiguous lysines and a farnesyl-ated cysteine. Results from biophysical studies in model systems suggest
that hydrophobic and electrostatic interactions are responsible for the
membrane binding properties of K-Ras.
The vascular endothelium is exposed to an array of physical forces, includ-ing shear stress via blood flow, contact with other cells such as neighboring
endothelial cells and leukocytes, and contact with the basement membrane.
Endothelial cell morphology, protein expression, stiffness and cytoskeletal
arrangement are all influenced by these mechanochemical forces.
In 1996, the Committee on Population of the National Research Council
sponsored a novel workshop on the biodemography of aging, which
resulted in the volume Between Zeus and the Salmon: The Biodemography
of Longevity (National Research Council, 1997). The workshop and its
report, which considered the continuing increases in human life span in a
broad biological context, launched a new phase in studies of human aging
at the population level.
The structure and membrane interaction of the internal
fusion peptide (IFP) fragment of the avian sarcoma and
leucosis virus (ASLV) envelope glycoprotein was studied by
an array of biophysical methods. The peptide was found to
induce lipidmixing of vesicles more strongly than the fusion
peptide derived from the N-terminal fusion peptide of
influenza virus (HA2-FP). It was observed that the helical
structure was enhanced in association with the model
membranes, particularly in the N-terminal portion of the
The high water permeability of certain biological membranes is
due to the presence of aquaporin water channel proteins. AQP1
was discovered in human red cells. AQP1 has been thoroughly
characterized biophysically, and the atomic structure of AQP1
has been elucidated. Ten homologs have been identified in
humans. These are selectively permeated by water (aquaporins)
or water plus glycerol (aquaglyceroporins). The sites of expres-sion predict the clinical phenotypes in humans. Individuals lack-ing Colton blood group antigens have mutations in the AQP1
Most of the biochemical and biophysical processes of proteins take place
at membranes, and are thus under the influence of strong local electric
fields, which are likely to affect the structure as well as the reaction mecha-nism and dynamics.
A great deal must still be learnt on the structural features of amyloid
assemblies, particularly prefibrillar aggregates, and the relationship of the
latter with amyloid cytotoxicity. Presently, it is recognized that the popula-tion of unstable, heterogeneous amyloid oligomers and protofibrils is
mainly responsible for amyloid cytotoxicity.
Our laboratory is interested in the biochemical and biophysical
basis of cell structure. The structure of a cell is determined
primarily by its cytoskeleton, which serves as a scaffold to sup-port the plasma membrane, and as a network of tracks along
which motor proteins transport sub cellular structures. Our
research is therefore focused on the mechanics of the cytoskele-ton, with a particular emphasis on microtubules and microtu-bule-based motors.
Dynamin, a protein playing crucial roles in endocytosis, oligomerizes to
form spirals around the necks of incipient vesicles and helps their scission
from membranes. This oligomerization is known to be mediated by the
GTPase effector domain (GED). Here we have characterized the structural
features of recombinant GED using a variety of biophysical methods.
Reconstitution of membrane proteins allows their study in a
membrane environment that can be manipulated at will.
Because membrane proteins have diverse biophysical pro-perties, reconstitution methods have so far been developed
for individual proteins on an ad hoc basis. We developed a
postinsertion reconstitution method for CCR5, a G protein
coupled receptor, with seven transmembraneahelices and
small ecto- and endodomains.
The adenosine A2a
receptor belongs to the seven trans-membrane helix G-protein-coupled receptor family, is
abundant in striatum, vasculature and platelets and is
involved in several physiological processes such as blood
pressure regulation and protection of cells during anoxia.
For structural and biophysical studies we have expressed
the human adenosine A2areceptor (hA2aR) at high levels
inserted into the Escherichia coliinner membrane, and
established a puri®cation scheme.