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SAPK

Definition

Definition

Saccharomyces cerevisiae is a unicellular fungi (yeast) that is a useful tool in biotechnology (production of bread, beer and wine) and model organism in cell biology, e.g. in the study of the cell cycle or trafficking (like ! endocytosis or ! autophagy).

Stress-activated protein kinase (SAPK), also known as JNK, is responsible for phosphorylation of c-Jun and ATF-2 proteins in response to cellular stress; ! AP-1.

SAM Definition Sterile alpha motif (SAM) domain is a protein interaction domain of around 70 amino acids present in many diverse signaling proteins. SAM domains have been shown to self associate in some systems.

Sanctuary Site Definition A sanctuary site is any location in the body that is poorly penetrated by drugs. Presumably, the brain is protected from antileukemic drugs by the blood-brain barrier.

SARA Definition Smad anchor for receptor activation (SARA) is a cytosolic protein anchored in membranes close to TGFb receptors. This protein presents unphosphorylated R-Smads to TGFb-activated receptor complexes.

Sarcoma Definition Sarcoma is a malignant tumor of mesenchymal origin.

Satellite DNA Definition Satellite DNA consists of many tandem repeats (identical or related) of a short basic repeating unit.

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Scatter Factor

Scatter Factor Eliot M. Rosen, Saijun Fan, Itzhak D. Goldberg Long Island Jewish Medical Center, and Albert Einstein College of Medicine, Bronx, New York, USA [email protected]

Synonyms *

hepatocyte growth factor (HGF)

Definition Scatter factor (SF), also known as hepatocyte growth factor (HGF), is a multifunctional cytokine that participates in various biologic processes, including: embryonic development (! morphogenesis), oncogenesis (tumor formation), ! angiogenesis (new blood vessel formation), and the regulation of ! apoptosis (programmed cell death). SF was originally characterized as a protein secreted by mesenchymal cells (e.g. fibroblasts) that disperses (or `scatters') contiguous sheets of epithelium and stimulates cell motility. HGF was identified as a serum-derived protein that stimulates the proliferation of adult rat hepatocytes. Subsequent studies revealed that SF and HGF are identical. HGF is the ligand of a ! tyrosine kinase receptor encoded by a ! proto-oncogene (c-! Met), HGF binding causes receptor activation.

Characteristics SF is a heparin-binding glycoprotein composed of a 60 kD a-chain and a 30 kD b-chain. The achain is composed of an N-terminal hairpin loop, followed by four ! kringle domains (looped structures that mediate protein interactions). The b-chain resembles protein-degrading enzymes such as trypsin, but SF lacks protein-degrading activity due to two key amino acid substitutions at the catalytic center. The binding of heparin to SF modulates its biologic activity, protects it from degradation and allows it to be stored in the extracellular matrix. Several shortened forms of SF containing only the Nterminal loop and the first kringle domain

(NK1) or the first two kringle domains (NK2) are sufficient to bind wi