biochemistry Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology and ...

, an effector molecule is usually a

small molecule Within the fields of molecular biology and pharmacology, a small molecule or micromolecule is a low molecular weight (≤ 1000 daltons) organic compound that may regulate a biological process, with a size on the order of 1 nm. Many drugs ...

that selectively binds to a protein and regulates its biological activity. In this manner, effector molecules act as ligands that can increase or decrease

enzyme activity Enzyme assays are laboratory methods for measuring enzymatic activity. They are vital for the study of enzyme kinetics and enzyme inhibition. Enzyme units The quantity or concentration of an enzyme can be expressed in molar amounts, as with a ...

, gene expression, or

cell signaling In biology, cell signaling (cell signalling in British English) or cell communication is the ability of a cell to receive, process, and transmit signals with its environment and with itself. Cell signaling is a fundamental property of all cellula ...

. Effector molecules can also directly regulate the activity of some

mRNA In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein. mRNA is created during the ...

molecules (

riboswitch In molecular biology, a riboswitch is a regulatory segment of a messenger RNA molecule that binds a small molecule, resulting in a change in production of the proteins encoded by the mRNA. Thus, an mRNA that contains a riboswitch is directly in ...

es). Other examples of effector functions in biochemistry include

hormone signaling A hormone receptor is a receptor (biochemistry), receptor molecule that binds to a specific chemical messenger . Hormone receptors are a wide family of proteins made up of receptors for thyroid and steroid hormones, retinoids and Vitamin D, and a v ...

and

immune response An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders. These invaders include a wide variety of different microorganisms including viruses, bacteria, parasites, and fungi which could ...

. In some cases, specific proteins serve the same role as effector molecules (note:

s refers to organic compounds similar in size to amino acids or RNA strands. Most effector molecules are therefor much smaller than individual proteins, which consist of many amino acids). One example of this is in cellular signal transduction cascades. The term ''effector'' is used in other fields of biology. For instance, the effector end of a

neuron A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. ...

is the terminus where an axon makes contact with the muscle or organ that it stimulates or suppresses.

Examples

Antibody Effectors are effectors involved with the production and secretion of molecules involved in pathogen defense, such as Immunoglobulin. Many antibodies then act as effector molecules for the immune system of the organism, typically as enzyme activators. Allosteric effectors can bind to regulatory proteins involved in

RNA transcription Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules called ...

in order to change its activity. In this way activator proteins become active to bind to the DNA to promote RNA Polymerase and

repressor proteins In molecular genetics, a repressor is a DNA- or RNA-binding protein that inhibits the expression of one or more genes by binding to the operator or associated silencers. A DNA-binding repressor blocks the attachment of RNA polymerase to th ...

become inactive and RNA polymerase can bind to the DNA.

Bacterial effector protein Bacterial effectors are proteins secreted by pathogenic bacteria into the cells of their host, usually using a type 3 secretion system (TTSS/T3SS), a type 4 secretion system (TFSS/T4SS) or a Type VI secretion system (T6SS). Some bacteria inject on ...

s are injected by (usually

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

ic) bacterial cells into the cells of their host. The injected proteins serve different functions dependent on the bacteria of origin, but typically serve the purpose of inhibiting the host cells immune response. Fungal effectors are secreted by pathogenic or beneficial fungi into and around host cells by invasive hyphae to disable defense components or facilitate colonization. Protein secretion systems in fungi involve the

Spitzenkörper The Spitzenkörper (German for pointed body, SPK) is a structure found in fungal hyphae that is the organizing center for hyphal growth and morphogenesis. It consists of many small vesicles and is present in growing hyphal tips, during spore ger ...

. Plant pathogenic fungi use two distinct effector secretion systems and each secretory pathway is specific to an effector family: * apoplastic effectors : proteins which stay into the

apoplast Inside a plant, the apoplast can mean the space outside of cell membranes, where material can diffuse freely; that is, the extracellular spaces. ''Apoplast '' can also refer especially to the continuum of cell walls of adjacent cells; fluid and ...

, they are translocated and accumulated into a distinct compartment enclosing the growing hypha named the EIHM (extra-invasive hyphal membrane). * cytoplasmic effectors : proteins which enter the host cytoplasm, they are accumulated into a complex plant-derived structure named the biotrophic interfacial complex (BIC) and they are later translocated across the EIHM inside the plant cell. It has been shown that cytoplasmic effectors can move through a few layers of plant cells, probably a way to prepare them for hyphal invasion.

Types

Enzyme activator Enzyme activators are molecules that bind to enzymes and increase their activity. They are the opposite of enzyme inhibitors. These molecules are often involved in the allosteric regulation of enzymes in the control of metabolism. An example of a ...

Enzyme inhibitor An enzyme inhibitor is a molecule that binds to an enzyme and blocks its activity. Enzymes are proteins that speed up chemical reactions necessary for life, in which substrate molecules are converted into products. An enzyme facilitates a sp ...

References

Biology terminology {{Protein-stub