Chapter 35. Molecular Motors Flashcards
Substances, such as glucose, that, when present in the form of a gr adient, cause bacteria to swim toward the source of the gradient.
Chemoattractant
The process of moving in specific directions in response to environmental cues.
Chemotaxis
Proteolytic digestion products of myosin that are the force-generating units of the intact myosin molecule; the S1 fragment contains the ATPase and actin-binding sites.
S1 fragment
A bundle of microtubules which is composed of a peripheral group of nine microtubule pairs surrounding two singlet microtubules.
axoneme
The ability of the immune system to respond more rapidly and effectively to pathogens that have been encountered previously.
Immunological memory
Internal scaffolding of cells, made up of microfilaments, intermediate filaments, and microtubules, which enables cells to transport vesicles, change shape, and migrate.
Cytoskeleton
A bacterial flagellar protein that is part of the MS (membrane and supramembrane) ring; FliG, in combination with flagellar proteins MotA/MotB, forms a proton channel that drives the rotation of the flagellum.
FliG
A highly conserved protein found in all eukaryotes; in striated muscle, it forms the thin filaments of the sarcomere and activates the ATPase of myosin.
Actin
Actin monomers that come together to form filaments called F-actin.
G-actin
A property of microtubules such that some microtubules in a population lengthen while other simultaneously shorten; a result of the random fluctuations in the number of GTP- tubulin subunits or GDP-tubulin subunits at the ends of the microtubule. GTP-tubulin polymerizes more readily.
Dynamic instability
A short segment of kinesin that binds to the head domain of kinesin when ATP is bound and is released when the nucleotide-binding site is vacant or occupied by ADP.
Neck linker
A filament of G-actin monomers that is a polar, self-assembling, dynamic polymer.
F-actin
Vaccines that contain pathogens that have been rendered harmless by treatment with chemicals or high heat.
Killed, or inactivate, vaccines
A protein that forms the thick filaments of striated muscle; displays ATPase activity at its globular head, which, in conjunction with the ability to reversibly bind actin at its fibrous region, provides the power stroke of muscle contraction.
Myosin
A long helix that connects the switch regions of the S1 fragment to the lever arm; the nature of the nucleotide in the S1 fragment (ATP or ADP) allows the relay helix to change position, resulting in a reorientation of the lever arm.
Relay helix
A large protein with ATPase activity that is a component of microtubules; the ATPase activity provides the power for the movement of cilia and flagella. In cytoplasm, a motor protein that is related to the dynein in flagella and cilia and powers retrograde transport
Dynein
Potentially harmful substances, such phenol, that, when present in the form of a gradient, cause bacteria to swim away from the source of the gradient.
Chemorepellant
Located in the thin filaments of a sarcomere, a protein that plays a role in the regulation of muscle contraction by blocking the interaction of myosin with actin at low Ca2+ concentrations; regulated by troponin.
Tropomyosin
A motor protein, built around a P-loop NTPase core, that has several structural features in common with myosin; conventional kinesin moves toward the plus end of microtubules.
Conventional kinesin
A long helix that protrudes from the S1 fragment of myosin to bind the light chains; amplifies small structural changes at the nucleotide-binding site of myosin to achieve 110-Å movement along an actin filament.
Lever arm
The conformational change in myosin heads powered by phosphate release as myosin binds to actin and pulls the actin filament, with the resulting displacement of the myosin heads.
Power stroke
The concentration of G-actin monomers above which polymerization occurs and below which depolymerization occurs. The critical concentration is equal to the dissociation constant (Kd) of an actin monomer from a filament.
Critical concentration
The functional unit of a myofibril; its distinct repeating structure is due to the overlapping of thick protein filaments, composed of myosin, and thin filaments, composed of actin and other proteins, which contract through the use of a sliding-filament method.
Sarcomere
One of the two protein filaments present in a myofibril, which have diameters of about 15 nm and consist primarily of myosin.
thick filaments
A cytoskeleton element that is a major component of cilia, eukaryotic flagella, and the mitotic spindle; composed primarily of alpha- and beta-tubulin; capable of rapid assembly and disassembly.
Microtubule
One of the two protein filaments present in a myofibril, which have diameters of approximately 8nm and consist of actin as well as tropomyosin and the troponin complex.
thin filaments
A pair of bacterial proteins that form a ring around the base of the flagellum and, in conjunction with FliG, form a proton channel that drives the rotation of the flagellum.
MotA-MotB pair
The protein component of bacterial flagella.
Flagellin
A protein in the bacterial chemotaxis signaling pathway that, when phosphorylated, leads to clockwise rotation of the flagellum, causing tumbling, and that, when dephosphorylated, leads to counterclockwise rotation and smooth swimming.
CheY
A means of measuring the force exerted by a single myosin molecule on an actin filament.
Optical trap
A protein with ATPase activity that moves cellular organelles along microtubule tracks in anterograde transport.
Kinesin
Fibrils inside the cytosol of vertebrate muscle cells that give such cells their striated appearance; the functional unit of a myofibril is a sarcomere.
Myofibril
Vaccines that contains live pathogens that have accumulated mutations so that they are no longer virulent to human cells.
Live attenuated vaccines
Vaccines that contain a purified protein component of a pathogen.
Subunit vaccines
Vaccines that are used against pathogens that employ an extracellular toxin to cause disease. These vaccines contain a form of the toxin that has been inactivated by treatment with chemicals or high heat.
Toxoid vaccines
The major microtubule protein component that exists in two forms, alpha- and beta-tubulin; tubulins display GTPase activity that is vital for the assembly and disassembly of microtubules.
Tubulin
Located in the thin filaments of the sarcomeres, that regulate muscle contraction through allosteric interactions with tropomyosin in response to changes in Ca2+ concentrations.
Troponin complex
