Martin Klingenberg

Martin Klingenberg was born on 5 December 1928 in Rostock, Germany, the younger son of the pastor Paul Klingenberg (born 1895). His elder brother Wilhelm Klingenberg became a well known mathematician. Martin Klingenberg studied chemistry, and in 1954 he went to the United States as a postdoctoral researcher at the Johnson Foundation of the University of Pennsylvania in Philadelphia. He later recalled that his first task there was to build his own set of glass micropipettes, which at that time were filled by mouth.

In 1956 Klingenberg joined the group of Theodor Bücher, director of the Institute of Physiological Chemistry at the University of Marburg. Bücher's group was developing optical enzyme assays, and it was there that Klingenberg witnessed his colleague Heinrich Schnitger invent the piston-driven micropipette with a disposable plastic tip, the forerunner of the instrument now used in laboratories worldwide.

Klingenberg's own research focused on mitochondria, and above all on how metabolites cross the inner mitochondrial membrane. His work in the 1960s helped show that ATP made inside the mitochondrion is exported to the cytosol in a one-for-one exchange against ADP, a process controlled by the membrane potential. By studying how nucleotides and the inhibitors atractyloside and bongkrekic acid bind to the carrier, his group revealed that its binding site reorients between the outer and inner faces of the membrane. He received the Adolf Fick Prize in 1964.

At the Ludwig-Maximilians-Universität in Munich he became professor and holder of the chair of Physical Biochemistry at the Institute of Physiological Chemistry. His laboratory isolated the intact ADP/ATP carrier, the first transporter of any kind to be purified, which allowed transport to be rebuilt in artificial membranes and studied free of the complications of whole mitochondria. In the early 1980s his group determined the complete amino acid sequence of the carrier from beef heart mitochondria, the first sequence of any eukaryotic carrier, and proposed a model of six helices crossing the membrane. Later work with reconstituted carrier measured the electrical currents of nucleotide transport.

From the late 1970s Klingenberg also studied the uncoupling protein (UCP1) of brown fat, which lets mitochondria release energy as heat. In 1985 his group showed that the uncoupling protein is related to the ADP/ATP carrier, pointing to a whole family of mitochondrial carriers. This research drew growing interest as the pharmaceutical industry looked for treatments for obesity. In 1981 he received the Otto Warburg Medal. He retired in 1999 and was succeeded in the chair, now the Chair of Metabolic Biochemistry at the Biomedical Center, by Christian Haass.

Klingenberg came from a clergy family in Rostock and was the brother of the mathematician Wilhelm Klingenberg. He lived and worked in Munich for most of his career. Former colleagues remembered that his scientific curiosity remained undiminished long after he became emeritus: he continued to publish, including a long survey of ADP and ATP transport in 2008 and work on cardiolipin and mitochondrial carriers in 2009. Few other details of his private life have been published.

Martin Klingenberg died on 3 October 2026, aged 97. A death notice was published in the Süddeutsche Zeitung on 10 October 2026. On 5 October the Chair of Metabolic Biochemistry at the LMU published an obituary by Christian Haass on behalf of the chair and all of Klingenberg's former staff, describing him as an outstanding biochemist and an internationally pioneering scientist in mitochondrial bioenergetics. The cause and place of his death were not made public.

Klingenberg's work made the mitochondrial ADP/ATP carrier one of the most thoroughly characterised membrane transporters, and it remains central to the modern understanding of how energy made in mitochondria is delivered to the rest of the cell. His isolation of the carrier, its sequence and his model of a single binding site that switches sides laid foundations for the study of the whole mitochondrial carrier family, while his research on uncoupling proteins contributed to the study of heat production in brown fat and of metabolism and obesity. In 2018 former colleagues marked his four decades of research on uncoupling proteins with a review in Archives of Biochemistry and Biophysics. His 2005 essay on the invention of the micropipette preserved an eyewitness account of the origin of one of the most common tools in modern biology.