Biology Reference
In-Depth Information
sequences. However, the manual annotation effort carried out by Swiss-
Prot is mainly concentrated on proteins from model organisms to ensure
the presence of high-quality annotation for representative members of
most protein families. What makes Swiss-Prot unique is that it strives to
present a high-quality synthetic view of the knowledge that is available
on a particular protein.
2
This requires the expertise of a dedicated set
of curators who extract, from the scientific literature, information that
will be summarized and integrated into the knowledgebase. Curators
also make use of state-of-the-art bioinformatics sequence analysis tools
and, together with information gleaned from the scientific community,
aim to help bench scientists through accurate protein annotation.
Currently, Swiss-Prot contains about 400 000 reviewed (annotated)
entries; while TrEMBL contains more than 6 million unreviewed,
computer-annotated entries.
1.2. What is Dictyostelium discoideum?
Dictyostelium discoideum
is one of the few organisms selected by the
National Institutes of Health (NIH) as a suitable model organism for
functional analysis of sequenced genes. It is a unicellular ameba dur-
ing most of its life cycle, but starvation induces a unique developmen-
tal program during which individual cells aggregate by a chemotactic
response to a cAMP gradient to form a multicellular entity. A mor-
phogenetic process involving cell migration and cellular morphogene-
sis then transforms a simple mound of cells into a slug called
pseudoplasmodium, establishing a relatively simple developmental
pattern. This structure further develops into a fruiting body consisting
of multiple terminally differentiated cell types, including spores and
stalk cells.
3
These unique features of
D. discoideum
— together with
its easy and efficient genetic manipulation by gene targeting, gene
replacement, insertional mutagenesis, and suppressor screens — have
made it a popular experimental system for the study of cytokinesis,
motility, phagocytosis, chemotaxis, cell sorting, pattern formation,
and cell-type determination. Many of these cellular behaviors and bio-
chemical mechanisms are either absent or less accessible to experi-
mental studies in other model organisms.