Yama/CPP32β, a mammalian homolog of CED-3, is a CrmA-inhibitable protease that cleaves the death substrate poly(ADP-ribose) polymerase

Caspases, which are the executioners of apoptosis, comprise two distinct classes, the initiators and the effectors. Although general structural features are shared between the initiator and the effector caspases, their activation, inhibition and release of inhibition are differentially regulated. Biochemical and structural studies have led to important advances in understanding the underlying molecular mechanisms of caspase regulation. This article reviews these latest advances and describes our present understanding of caspase regulation during apoptosis.

Molecular mechanisms of caspase regulation during apoptosis

Heparin, a sulfated polysaccharide belonging to the family of glycosaminoglycans, has numerous important biological activities, associated with its interaction with diverse proteins. Heparin is widely used as an anticoagulant drug based on its ability to accelerate the rate at which antithrombin inhibits serine proteases in the blood coagulation cascade. Heparin and the structurally related heparan sulfate are complex linear polymers comprised of a mixture of chains of different length, having variable sequences. Heparan sulfate is ubiquitously distributed on the surfaces of animal cells and in the extracellular matrix. It also mediates various physiologic and pathophysiologic processes. Difficulties in evaluating the role of heparin and heparan sulfate in vivo may be partly ascribed to ignorance of the detailed structure and sequence of these polysaccharides. In addition, the understanding of carbohydrate-protein interactions has lagged behind that of the more thoroughly studied protein-protein and protein-nucleic acid interactions. The recent extensive studies on the structural, kinetic, and thermodynamic aspects of the protein binding of heparin and heparan sulfate have led to an improved understanding of heparin-protein interactions. A high degree of specificity could be identified in many of these interactions. An understanding of these interactions at the molecular level is of fundamental importance in the design of new highly specific therapeutic agents. This review focuses on aspects of heparin structure and conformation, which are important for its interactions with proteins. It also describes the interaction of heparin and heparan sulfate with selected families of heparin-binding proteins.

http://www-heparin.rpi.edu/main/files/papers/4f1623c54d6ab5.21304086.pdf

Heparin-protein interactions

Almost one-third of all proteases can be classified as serine proteases, named for the nucleophilic Ser residue at the active site. This mechanistic class was originally distinguished by the presence of the AspHis-Ser “charge relay” system or “catalytic triad”.1 The Asp-His-Ser triad can be found in at least four different structural contexts, indicating that this catalytic machinery has evolved on at least four separate occasions.2 These four clans of serine proteases are typified by chymotrypsin, subtilisin, carboxypeptidase Y, and Clp protease (MEROPS nomenclature;3 Table 1). More recently, serine proteases with novel catalytic triads and dyads have been discovered, including Ser-His-Glu, Ser-Lys/His, His-Ser-His, and N-terminal Ser.2 Several of these novel serine proteases are subjects of accompanying articles in this issue. This article will review recent work on the mechanism and specificity of chymotrypsin-like enzymes, with the occasional references to pertinent experiments with subtilisin. Chymotrypsin-like proteases are the most abundant in nature, with over 240 proteases recognized in the MEROPS database.3 * E-mail: hedstrom@brandeis.edu; phone: 781-736-2333; FAX: 781-736-2349. 4501 Chem. Rev. 2002, 102, 4501−4523

Serine protease mechanism and specificity

The American Heart Association, in conjunction with the National Institutes of Health, annually reports the most up-to-date statistics related to heart disease, stroke, and cardiovascular risk factors, including core health behaviors (smoking, physical activity, diet, and weight) and health factors (cholesterol, blood pressure, and glucose control) that contribute to cardiovascular health. The Statistical Update presents the latest data on a range of major clinical heart and circulatory disease conditions (including stroke, congenital heart disease, rhythm disorders, subclinical atherosclerosis, coronary heart disease, heart failure, valvular disease, venous disease, and peripheral artery disease) and the associated outcomes (including quality of care, procedures, and economic costs).The American Heart Association, through its Statistics Committee, continuously monitors and evaluates sources of data on heart disease and stroke in the United States to provide the most current information available in the annual Statistical Update. The 2022 Statistical Update is the product of a full year's worth of effort by dedicated volunteer clinicians and scientists, committed government professionals, and American Heart Association staff members. This year's edition includes data on the monitoring and benefits of cardiovascular health in the population and an enhanced focus on social determinants of health, adverse pregnancy outcomes, vascular contributions to brain health, and the global burden of cardiovascular disease and healthy life expectancy.Each of the chapters in the Statistical Update focuses on a different topic related to heart disease and stroke statistics.The Statistical Update represents a critical resource for the lay public, policymakers, media professionals, clinicians, health care administrators, researchers, health advocates, and others seeking the best available data on these factors and conditions. 

https://www.ahajournals.org/doi/pdf/10.1161/CIR.0000000000001052

Heart Disease and Stroke Statistics—2022 Update: A Report From the American Heart Association

The serpins have evolved to be the predominant family of serine-protease inhibitors in man. Their unique mechanism of inhibition involves a profound change in conformation, although the nature and significance of this change has been controversial. Here we report the crystallographic structure of a typical serpin-protease complex and show the mechanism of inhibition. The conformational change is initiated by reaction of the active serine of the protease with the reactive centre of the serpin. This cleaves the reactive centre, which then moves 71 A to the opposite pole of the serpin, taking the tethered protease with it. The tight linkage of the two molecules and resulting overlap of their structures does not affect the hyperstable serpin, but causes a surprising 37% loss of structure in the protease. This is induced by the plucking of the serine from its active site, together with breakage of interactions formed during zymogen activation. The disruption of the catalytic site prevents the release of the protease from the complex, and the structural disorder allows its proteolytic destruction. It is this ability of the conformational mechanism to crush as well as inhibit proteases that provides the serpins with their selective advantage.

Structure of a serpin–protease complex shows inhibition by deformation

The maintenance of normal blood flow depends completely on the inhibition of thrombin by antithrombin, a member of the serpin family. Antithrombin circulates at a high concentration, but only becomes capable of efficient thrombin inhibition on interaction with heparin or related glycosaminoglycans. The anticoagulant properties of therapeutic heparin are mediated by its interaction with antithrombin, although the structural basis for this interaction is unclear. Here we present the crystal structure at a resolution of 2.5 A of the ternary complex between antithrombin, thrombin and a heparin mimetic (SR123781). The structure reveals a template mechanism with antithrombin and thrombin bound to the same heparin chain. A notably close contact interface, comprised of extensive active site and exosite interactions, explains, in molecular detail, the basis of the antithrombotic properties of therapeutic heparin.

Structure of the antithrombin–thrombin–heparin ternary complex reveals the antithrombotic mechanism of heparin

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1538-7836.2007.02516.x

Serpins in thrombosis, hemostasis and fibrinolysis

Structure and properties of ovalbumin.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1538-7836.2011.04360.x

James A. Huntington

Papers

Structure of a serpin–protease complex shows inhibition by deformation

Structure of the antithrombin–thrombin–heparin ternary complex reveals the antithrombotic mechanism of heparin

Serpins in thrombosis, hemostasis and fibrinolysis

Structure and properties of ovalbumin.

Serpin structure, function and dysfunction.